Signal strength enhancement in a biometric sensor array

ABSTRACT

A biometric imager may comprise a plurality of sensor element traces formed in or on a sensor substrate which may comprise at least a portion of a display screen defining a biometric sensing area and forming in-active pixel locations; an auxiliary active circuit formed in or on the sensor substrate on the periphery of the biometric sensing area and in direct or indirect electrical contact with the sensor element traces; and providing a signal processing interface to a remotely located controller integrated circuit. The sensor element traces may form a portion of one dimensional linear sensor array or pixel locations in a two dimensional grid array capacitive gap biometric imaging sensor. The auxiliary circuit may provide pixel location selection or pixel signal amplification. The auxiliary circuit may be mounted on a surface of the display screen. The auxiliary circuit further comprising a separate pixel location selection controller circuit.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is a continuation of copending U.S. patentapplication Ser. No. 14/880,887, filed Oct. 12, 2015, which is acontinuation of U.S. patent application Ser. No. 14/339,656, filed Jul.24, 2014, issued as U.S. Pat. No. 9,158,958 entitled SIGNAL STRENGTHENHANCEMENT IN A BIOMETRIC SENSOR ARRAY, which claims the benefit ofU.S. Provisional Patent Application Nos. 61/858,067, filed Jul. 24,2013, entitled BIOMETRIC SENSOR ON GLASS PACKAGINGS AND HOUSINGS ANDMETHODS THEREFOR, and 61/858,017, filed Jul. 24, 2013 entitled SIGNALSTRENGTH ENHANCEMENT IN A BIOMETRIC SENSOR ARRAY, all of which areincorporated herein by reference.

The present application is related to pending U.S. patent applicationSer. No. 12/914,812, filed on Oct. 28, 2010, entitled INTEGRATEDFINGERPRINT SENSOR AND DISPLAY, Pub. No. US 2011/0102567 A1, publishedon May 5, 2011; Ser. No. 12/916,000, filed on Oct. 29, 2010, entitledSYSTEMS AND METHODS FOR SENSING FINGER PRINTS THROUGH A DISPLAY, Pub.No. US 2011/0102569 A1, published on May 5, 2011; Ser. No. 13/099,983,filed on May 3, 2011, entitled FINGERPRINT SENSOR AND INTEGRATABLEELECTRONIC DISPLAY, Pub. No. US 2011/0267298 A1, published on Nov. 3,2011; Pub. No. US 2012/0242635 A1 published Sep. 27, 2012, entitledFINGERPRINT SENSOR AND INTEGRATABLE ELECTRONIC DISPLAY, Pub. No. US2012/0242635 A1, published on Sep. 27, 2012; Pub. No. US 2013/0169590A1, published Jul. 4, 2013, entitled STRUCTURES AND MANUFACTURINGMETHODS FOR GLASS COVERED ELECTRODE DEVICES, Pub. No. US 2013/0169590A1, published on Jul. 4, 2013; Pub No. US 2013/0265137 A1, publishedOct. 10, 2013, entitled INTEGRATABLE FINGERPRINT SENSOR PACKAGINGS; Pub.No. US 2014/0103943 A1, published Apr. 17, 2014, entitled FINGERPRINTSENSOR AND BUTTON COMBINATIONS AND METHODS OF MAKING SAME, thedisclosures of each of which are hereby incorporated by reference.

BACKGROUND

Biometric authentication systems are used for authenticating users.Biometric sensing technology provides a reliable, non-intrusive way toverify individual identity for authentication purposes.

Fingerprints, like various other biometric characteristics, are based onunalterable personal characteristics and thus are a reliable mechanismto identify individuals. There are many potential applications forutilization of biometric and fingerprints sensors. For example,electronic fingerprint sensors may be used to provide access control instationary applications, such as security checkpoints. Electronicfingerprint sensors may also be used to provide access control inportable applications, such as portable computers, personal dataassistants (PDAs), cell phones, gaming devices, navigation devices,information appliances, data storage devices, and the like. Accordingly,some applications, particularly portable applications, may requireelectronic fingerprint sensing systems that are compact, highlyreliable, and inexpensive.

Various electronic fingerprint sensing methods, techniques, and deviceshave been proposed and/or are currently in use or under development. Forexample, optical and capacitive fingerprint sensing devices arecurrently on the market. Like a digital camera, optical technologyutilizes visible light to capture a digital image. In particular,optical technology may use a light source to illuminate an individual'sfinger while a sensor, e.g., a charge-coupled device (“CCD”) captures ananalog image. This analog image may then be converted to a digitalimage. Other sensors may be pressure based, e.g., using piezoelectricmaterials or deformable capacitive sensors, impedance based, such asresistive sensors, heat based, etc.

There are generally two types of capacitive fingerprint sensingtechnologies: passive and active. Both types of capacitive technologiescan utilize similar principles of capacitance changes to generatefingerprint images. Passive capacitive technology typically utilizes alinear one-dimensional (1D) or a two-dimensional (2D) array of plates(i.e., electrodes or traces) to apply an electrical signal, e.g., in theform of an electrical field, such as a varying high speed (radiofrequency (“RF”) or the like) signal transmitted to the finger of theuser from a transmitter trace and received at a receiver trace afterpassage through the finger. A variation in the signal caused by theimpedance of the finger indicates, e.g., whether there is a fingerprintvalley or ridge between the transmitter trace and the receiver trace inthe vicinity of where the transmission and reception between the tracesoccurs. Fingerprint ridges, as an example, can typically display farless impedance (lower capacitance across the gap) than valleys, whichmay exhibit relatively high impedance (higher capacitance across thegap). The gaps can be between traces on the same plane, horizontal, orin different planes, vertical.

Active capacitive technology is similar to passive technology, but mayrequire initial excitation of the epidermal skin layer of the finger byapplying a current or a voltage directly to the finger. Typically,thereafter, the actual change in capacitance between the source of thevoltage or current on an excitation electrode (trace) and anotherreceptor electrode (trace) is measured to determine the presence of avalley or ridge intermediate the source electrode and the anotherreceptor electrode. Active capacitive sensors, however, may be adverselyaffected by such effects as dry or worn finger print components. Bycontrast, passive sensors are typically capable of producing imagesregardless of contact resistance and require significantly less power,e.g., because of more penetration of the layer of skin of the user inthe vicinity of the transmitter/receiver pair.

In some embodiments the traces may form a plurality of transmitterelectrodes and a single receiver electrode or a plurality of receiverelectrodes and a single transmitter electrode arranged in a linear onedimensional capacitive gap array. In such embodiments the capacitivegape may be horizontal across the gap formed by the respective ends ofthe plurality of traces and the single trace, whether transmitter orreceiver. Advantageously such sensor systems can be very compact,inexpensive to manufacture, with the sensor element traces simply formedon a substrate, such as a flexible substrate, made of, e.g., Kapton®tape made by 3M, and reliable, e.g., due to insulation of the finger ofthe user from the traces and/or electric contact, etc.

In some embodiments, the traces may form a 2D grid array, e.g., withrows of transmitter/receiver traces on one substrate and columns ofreceiver/transmitter traces on the same or a separate substrate, e.g.,laminated together with some form of dielectric between the traces toform a 2D sensor element array. Such 2D arrays may be essentially aslong as the last digit of the finger forming a placement sensor elementarray, or shorter in the direction of the length of the finger, forminga swiped 2D array. While both the 1D linear array sensors systems andthe 2D array sensor systems can operate in essentially the same way,i.e., with transmission of a signal from a transmitter trace to areceiver trace, the 2D arrays are larger in the region that must beexposed in the vicinity of the finger being sensed, and are generallymore complex electronically. In addition such 2D arrays can involvehigher degrees of noise and other impediments to accurate signalprocessing of the received signals and also more complicated softwareand hardware for reconstructing the fingerprint from a series of swiped2D images accumulated during sensing in the direction of the finger andsensor elements relative movement during the swipe.

Although each of the fingerprint sensing technologies described abovemay generate satisfactory fingerprint images, each may be adverselyaffected by noise, interference, and other effects. For example,capacitive sensors may be particularly susceptible to noise andparasitic capacitive coupling, which may degrade the quality of theacquired fingerprint image. 2D arrays may be more so susceptible thanlinear 1D arrays. Prior attempts to reduce noise in 2D sensors haveemployed reference capacitors positioned at each sensor pixel to providea method of subtracting noise contributions that affect both the fingercapacitance and the reference capacitor. This technique is mosteffective for electrical noise at the pixel level, as seen, e.g., inU.S. Pat. No. 8,115,497B2, PIXEL SENSING CIRCUIT WITH COMMON MODECANCELLATION, issued on Feb. 14, 2012, to Gozzini, and/or US Pub. No. US2012/0085822 A1, entitled FINGER SENSING DEVICE INCLUDING DIFFERENTIALMEASUREMENT CIRCUITRY AND RELATED METHODS, published on Apr. 12, 2012,referenced above. Also proposed has been the user of a referenceelectrode external to the sensor array, e.g., that is not affected by anactual presence of the finger of a user, such as is discussed in U.S.Pat. No. 8,421,890 B2, entitled ELECTRONIC IMAGER USING AN IMPEDANCESENSOR GRID ARRAY AND METHOD OF MAKING, issued to Benkley on Apr. 16,2013. Accordingly, it would be an advance in the art to reduce theeffects of noise, parasitic capacitive coupling, and other effects incapacitive-type fingerprint sensing circuits.

Two-dimensional matrix format fingerprint readers have historically beenbuilt with row and column multiplexing circuits along the edge of thesensor pixel array, e.g., as illustrated in U.S. Pat. No. 7,616,786 B2,entitled FINGER BIOMETRIC SENSOR WITH SENSOR ELECTRONICS DISTRIBUTEDOVER THIN FILM AND MONOCRYSTALLINE SUBSTRATES AND RELATED METHODS,issued to Setlak, et al., on Nov. 10, 2009; U.S. Pat. No. 7,835,553 B2,entitled IDENTITY AUTHENTICATION DEVICE AND FINGERPRINT SENSOR, issuedto Miyasaka on Nov. 16, 2010 and U.S. Pat. No. 7,755,369 B2, issued toChuang, et al. Mar. 23, 2010, entitled CAPACITIVE FINGERPRINT SENSOR ANDTHE PANEL THEREOF. This is true of both silicon substrate and glasssubstrate fingerprint readers. The use of such row and columnmultiplexing circuits all the signals to and from the individual rowsand columns to be carried over a small number of signal lines. This hasbeen done within a controller IC, but this makes the controller IC moreexpensive both from the standpoint of circuitry included in the IC andthus chip real estate utilized, as well as input/output connectionsrequired in the chip packaging.

According to co-pending U.S. Patent Pub US 2013/0177220 A1, entitledMETHODS AND DEVICES FOR CAPACITIVE IMAGE SENSING, published Jul. 11,2013, noise reduction in a 1D sensor array can be accomplished bysubtracting an NI (background) signal from the primary finger influenced(“FI”) signal as a means of subtracting out noise signals, e.g., thataffect adjacent receiver lines in a linear sensor.

The emergence of portable electronic computing platforms allowsfunctions and services to be enjoyed wherever necessary. Palmtopcomputers, personal digital assistants (“PDAs”), mobile telephones,portable game consoles, biometric/health monitors, and digital camerasare some everyday examples of portable electronic computing platforms.The desire for portability has driven these computing platforms tobecome smaller. Such portable electronic computing platforms, as well assome larger ones like lap top computer, pads and pods, electronictablets and the like have been increasingly shown to be in need ofauthentication of the user to access the device or once on the device toaccess applications running on the device and/or to access remoteapplications such as websites, web-pages, user accounts, such as emailof social network accounts, and engage in various forms of on-linetransactions, each requiring varying degrees of authentication of theuser to the device/application and the application to the user. Suchprocesses have increasingly required input from the user of userinformation, e.g., in the form of user name and password/PIN, but evenmore so more sophisticated and secure forms of user authentication tothe relying party and vice versa. For this purpose various forms ofbiometric user identification input, e.g., fingerprint authenticationinformation is being required.

It is difficult to efficiently collect user authentication inputinformation, e.g., fingerprint images or fingerprint authenticationdeterminations and the like on these ever-smaller personal computing andcommunication devices. In addition, such as portable electroniccomputing platforms need other forms of user inputs for multiplepurposes including, but not limited to, navigation: moving a cursor or apointer to a certain location on a display; selection: choosing, or notchoosing, an item or an action; and orientation: changing direction withor without visual feedback. Where the usual form of a GUI input device,e.g., an actual or virtual mouse may easily be used with and transportedwith a lap top computer or larger touch screen device, such as a tablet,smaller devices with concomitantly smaller display areas, such as cellphones, pads and pods, Blackberrys, etc. can be perfect candidates forsensors, such as biometric sensors and/or buttons and/or combinationsthereof that can perform authentication as well as act as GUI inputdevices.

Prior art systems have borrowed concepts for user input from much largerpersonal computers. Micro joysticks, navigation bars, scroll wheels,touch pads, steering wheels and buttons have all been adopted, withlimited success, in today's portable electronic computing platforms. Allof these devices consume substantial amounts of valuable surface realestate on a portable device. Mechanical devices such as joysticks,navigation bars and scroll wheels can wear out and become unreliable.Because they are generally physically designed for a single task, theytypically do not provide functions of other navigation devices. Theirsizes and required movement on or within the device often precludesoptimal ergonomic placement on portable computing platforms. Moreover,these smaller versions of their popular personal computer counterpartsusually do not offer accurate or high-resolution position information,since the movement information they sense is too coarsely grained.

Most commercially available biometric image sensors, such as fingerprintimage sensors that detect and measure features (e.g., valleys, ridges,and minutiae) on the surface of a finger using capacitive, thermal,optical, or other sensing technologies as noted above, fall into the twoabove noted categories: (1) full-size placement sensors and (2)typically smaller so-called swipe sensors, with the latter being either1D or 2D. Placement sensors have an active sensing surface that is largeenough to accommodate most of the interesting part of a finger at thesame time. Generally, they are rectangular in shape with a sensingsurface area of at least 100 mm2. The finger is held stationary whilebeing imaged on the full-placement sensor.

The other type of finger image sensor, called a swipe sensor, ischaracterized by a strip-like imaging area that is fully sized in onedirection (typically in length) but abbreviated in the other (typicallywidth). An example is the Atrua Wings ATW100 sensor, as described byAndrade in US Patent Application US 2003/0016849 A1 published Jan. 23,2003 (issued as U.S. Pat. No. 7,256,589 B2 on Aug. 14, 2007), and PCTpublication WO 02/095349. A finger is swiped across the sensor until allparts of it are imaged, analogous to how a feed through paper documentscanner operates. A sequence of slices or frames of the finger image iscaptured and processed to construct a composite image of the finger. Asshown in U.S. Pat. No. 7,099,496 B2, entitled SWIPED APERTURE CAPACITIVEFINGERPRINT SENSING SYSTEMS AND METHODS, issued to Benkley on Aug. 29,2006 shows a limiting case where the sensed “area” is a single linear 1Darray of capacitive gaps.

Several prior art devices use a touchpad for authenticating a user andmoving a cursor on a display device. A touchpad, which operatessimilarly to a finger image sensor, does not provide enough imageresolution or capability to distinguish ridges and valleys on thefingerprint. Instead, the touchpad perceives a finger as a blob andtracks the blob location to determine movement. Therefore, a touchpadcannot follow miniscule movements, nor can it very easily detectrotational movement.

U.S. Patent Publication No. US 2002/0054695 A1, titled “ConfigurableMulti-Function Touchpad Device,” to Bjorn et al. discloses a touchpadthat can be configured to authenticate a user or to control a cursor.The touchpad attempts to enhance the function of a touchpad to includefingerprint capability. It merely absorbs the hardware of a capacitivefinger image sensor into the much-larger size touchpad to achievecost-savings. It does not disclose using the finger image data of thedata collector for navigation or other device control. Moreover, asconceived, the apparatus of Bjorn, with its large size will preclude thetouchpad from being used in most portable electronic computingplatforms.

U.S. Pat. No. 6,408,087 B1, entitled CAPACITIVE SEMICONDUCTOR USER INPUTDEVICE, issued to Kramer on Jun. 18, 2002 discloses a system that uses afingerprint sensor to control a cursor on the display screen of acomputer. The system controls the position of a pointer on a displayaccording to detected motion of the ridges and pores of the fingerprint.The system has a number of limitations. It uses image-based correlationalgorithms and, unlike a system using a swipe sensor, requiresfingerprint images with multiple ridges, typical for capacitiveplacement sensors. To detect a motion parallel to the direction of aridge, the system requires the sensor to detect pores, a requirementrestricting its use to high-resolution sensors of at least 500 dpi. Thesystem detects changes in ridge width to sense changes of fingerpressure. However, ridge width measurement requires a veryhigh-resolution sensor to provide low-resolution of changes of fingerpressure. The algorithm is unique to emulating a mouse and is notsuitable for emulating other types of input devices, such as a joystickor a steering wheel, where screen movements are not always proportionalto finger movements. For example, a joystick requires a returning tohome position when there is no input and a steering wheel requiresrotational movement. The system is unique to capacitive sensors whereinverted amplifiers are associated with every sensor cell.

Capacitive fingerprint sensor arrays are often required to sense verysmall signals (e.g. associated with passive modification of atransmitted signal due to femtofarad differences in capacitance, e.g.,between a transmitter electrode (trace) and a receiver electrode (trace)due to the difference between the electric field passing from thetransmitter to the receiver through a finger of a user passing through aridge or a valley of the fingerprint of the user. This can be especiallyso when attempting to read a fingerprint through a somewhat thick coverlayer (0.100 mm or more, for example) of glass or other dielectricmaterial. In one-dimensional fingerprint sensors which use a lineararray of transmitters and a single receiver electrode, it has beensuggested that the signal strength on the receiver line can be boostedby activating multiple transmitters simultaneously transmitting to thesingle receiver or multiple receivers receiving from the singletransmitter trace, e.g., as discussed in co-pending US Patent Pub. US2013/0177220 A1, entitled METHODS AND DEVICES FOR CAPACITIVE IMAGESENSING, published Jul. 11, 2013.

Noise reduction methods have been proposed for 2D sensor arrays as well,as exemplified in U.S. Patent Pub. US 2013/0265137 A1 published Oct. 10,2013, entitled INTEGRATABLE FINGERPRINT SENSOR PACKAGINGS.

A similar problem(s) can exist for two-dimensional fingerprint sensorsas has been suggested for resolution in 1D linear sensor arrays, and theproblem may be further complicated by the additional parasiticcapacitances resulting from row/column crossovers that are not presentin a one-dimensional (linear) sensor array. In order to alleviate thisproblem, the vast majority of capacitive two-dimensional fingerprintsensors therefore incorporate not only the capacitive sensing electrodesin each sensor pixel, but also amplification circuitry to boost thesignal before it travels down the row or column line to a multiplexer orother readout circuit. The signal produced by the presence or absence ofa fingerprint ridge can be further boosted by combining the signals fromseveral receiver pixels adjacent to, or surrounding, a primarytransmitter pixel, as is discussed, e.g., in US Pub US 2012/0085822 A1,with named inventors Setlak et al., published on Apr. 12, 2012.

Fingerprint readers that are intended to be at least to a large degreetransparent are often fabricated on transparent glass. In this case therow and column drive and readout circuits may be contained in a siliconIC that is attached to, i.e., mounted on, the glass. However, the largenumber of rows and columns and fine pitch of these lines, especially onthe silicon IC, requires very high resolution die attach processes andconnector pads, or it may also make the silicon IC larger thannecessary, to fit all the input & output pads that are necessary. Forthis reason fingerprint readers built on glass substrates have beenbuilt all the necessary row/column multiplexing circuits (often as wellas sense amp circuits) in thin film transistor (“TFT”) circuitsfabricated directly on the glass, as shown, e.g., in U.S. Pat. No.7,616,786 B2, entitled FINGER BIOMETRIC SENSOR WITH SENSOR ELECTRONICSDISTRIBUTED OVER THIN FILM AND MONOCRYSTALLINE SUBSTRATES AND RELATEDMETHODS, issued to Setlak on Nov. 10, 2009, where the circuitry for anoperation amplifier is split between lower cost TFTs at the sensor arraylocation and higher performance transistors within a remotely mountedcontrol IC; U.S. Pat. No. 7,835,553 B2, entitled IDENTITY AUTHENTICATIONDEVICE AND FINGERPRINT SENSOR, issued to Miyakasa on Nov. 16, 2010, inwhich a fingerprint sensor array and local signal processing circuitryis contained in a separate housing separable from a user device andreplaceable as a unit; and U.S. Pat. No. 7,755,369 B2, entitledCAPACITIVE FINGERPRINT SENSOR AND THE PANEL THEREOF, issued to Chuang etal. on Jul. 13, 2010 in which all of the sensor circuitry, including thecontroller IC and in-pixel high performance circuitry, such asamplification is formed in or on the glass substrate of a display unit.Such TFT-on-glass fingerprint readers almost always include pixel selectand amplification circuitry at each array sensor pixel.

Two-dimensional capacitive fingerprint sensors can be more susceptibleto noise and the effects of parasitic capacitances due to their largersize and array structure as compared, e.g., to a one-dimensional (lineararray) sensor. For this reason virtually all current two-dimensionalfingerprint sensors incorporate in-pixel amplification, and perhapsother signal processing, circuitry. However, this means the sensor arraymust be made on a silicon wafer or with a technology (such as higherquality TFT technology, that can use, e.g., such high quality and thusmore expensive transistor fabrication technology, e.g., TFT fabricationtechnology, to provide high quality semiconductor devices such as may berequired for such transistors in each pixel. This increases the cost ofthe sensor substantially compared to a flex or glass based passivesensor matrix, e.g., where the electrodes (traces) forming the sensorelements are printed or etched on a substrate generally in a singlelayer process, more like printed circuit board (“PCB”) fabricationprocess.

SUMMARY OF THE DISCLOSED SUBJECT MATTER

An aspect of the disclosure is directed to a method of imaging abiometric object. Suitable methods comprise: utilizing a biometric imagesensor, comprising: a plurality of capacitive gap sensor electrodetraces forming an array of biometric sensor imaging pixel locationswithin a biometric sensing area of the biometric image sensor, at leastone of which sensor electrode traces forming a drive signal transmitterelectrode trace and at least one of which sensor electrode tracesforming a drive signal receiver electrode trace, wherein a change in adrive signal transmitted by a respective at least one drive signaltransmitter electrode trace and received by a respective at least onedrive signal receiver electrode trace is indicative of a biometric imagecharacteristic at the respective pixel location in the array, therespective drive signal transmitter electrode trace and respective drivesignal receiver electrode trace being formed on one of a single side ofa first substrate and on opposite sides of the first substrate;utilizing a controller contained in an integrated circuit mounted to asecond substrate remote from the biometric sensing area and inelectrical contact with the sensor electrode traces; utilizing anintermediate logic circuit intermediate, or formed between, thecontroller and the sensor electrode traces in the biometric sensingarea, which intermediate logic circuit is at least one of formed on thefirst substrate and formed on a third substrate mounted on the firstsubstrate, to control an activation sequence for a subset of theplurality of the capacitive gap sensor array pixel locations in responseto a single signal from the controller to the intermediate logiccircuit. Additionally, a change in a resulting signal received by the atleast one resulting signal receiver electrode trace is indicative of abiometric image characteristic at a respective pixel location in thearray. At least one of the sensor electrode traces can be configured toform a drive signal transmitter electrode and at least one of the sensorelectrode traces forming a resulting signal receiver electrode trace,the respective drive signal transmitter electrode and respectiveresulting signal receiver electrode trace being formed on one of asingle side of a first substrate and an opposite side of the firstsubstrate. Additionally, the first substrate and the second substratecan comprise a single substrate. In some configurations, the singlesubstrate can comprise one of a flexible dielectric and a glasssubstrate. In still other configurations, the single signal from thecontroller can comprise a first coded control signal causing theintermediate logic circuit to one of (1) individually address a firstsubset of the at least one drive signal transmitter electrode traces andprovide a drive signal to the respective drive signal electrode traceand (2) individually address a second subset of the at least one drivesignal receiver electrode traces and connect the respective drive signalreceiver electrode trace to an output of the biometric image sensor. Insome configurations, the single signal from the controller comprises afirst coded control signal, and in response to receiving the singlesignal the intermediate logic circuit is configured to individuallyaddress a subset of the at least one resulting signal receiver electrodetraces and communicatively couple the respective resulting signalreceiver electrode trace to an first input of the controller.Additionally, the single signal from the controller can comprise asecond coded control signal causing the intermediate logic circuit toboth individually address a third subset of the at least one drivesignal receiver electrode traces and provide a receiver electrode tracereceived signal to a first output of the intermediate logic circuit and(2) individually address a fourth subset of the at least one drivesignal receiver electrode traces and connect the respective drive signalreceiver electrode trace received signal to a second output of theintermediate logic circuit. In other configurations, the first outputcan comprise a first input to a differential amplifier and the secondoutput can comprise a second input to the differential amplifier. Forexample, the second coded control signal can comprise an output of ashift register set by the controller, connected to control logic routingrespective individual pixel location drive signal receiver electrodetraces to the respective first output or second output. The second codedcontrol signal can comprise an output of a shift register set by thecontroller, communicatively coupling the control logic routingrespective individual pixel location drive signal receiver electrodetraces to the respective first output or second output. Additionally,the intermediate logic circuit can comprise logic circuit transistorswitches formed on at least one of the first substrate and the thirdsubstrate. The logic circuit transistor can also be configured to suchthat the switch can comprise thin film transistors formed on the one ofthe first substrate and the third substrate. Additionally, theintermediate logic circuit can comprise a thin film transistor amplifierformed on one of the first substrate and the third substrateintermediate a respective drive signal receiver pixel location receiverelectrode trace and the intermediate logic circuit.

Another aspect of the disclosure is directed to a biometric objectimaging sensor comprising: a plurality of capacitive gap sensorelectrode traces forming an array of biometric sensor imaging pixellocations within a biometric sensing area of the biometric image sensor,at least one of which sensor electrode traces forming a drive signaltransmitter electrode trace and at least one of which sensor electrodetraces forming a drive signal receiver electrode trace, wherein a changein a drive signal transmitted by a respective at least one drive signaltransmitter electrode trace and received by a respective at least onedrive signal receiver electrode trace is indicative of a biometric imagecharacteristic at the respective pixel location in the array, therespective drive signal transmitter electrode trace and respective drivesignal receiver electrode trace being formed on one of a single side ofa first substrate and on opposite sides of the first substrate; acontroller contained in an integrated circuit mounted to a secondsubstrate remote from the biometric sensing area and in electricalcontact with the sensor electrode traces; an intermediate logic circuitintermediate the controller and the sensor electrode traces in thebiometric sensing area, which intermediate logic circuit is at least oneof formed on the first substrate and formed on a third substrate mountedon the first substrate, to control an activation sequence for a subsetof the plurality of the capacitive gap sensor array pixel locations inresponse to a single signal from the controller to the intermediatelogic circuit. The first substrate and the second substrate comprise asingle substrate. Additionally, the single substrate can comprise one ofa flexible dielectric and a glass substrate. In at least someconfigurations, the single signal from the controller can comprise afirst coded control signal causing the intermediate logic circuit to oneof (1) individually address a first subset of the at least one drivesignal transmitter electrode traces and provide a drive signal to therespective drive signal electrode trace and (2) individually address asecond subset of the at least one drive signal receiver electrode tracesand connect the respective drive signal receiver electrode trace to anoutput of the biometric imaging sensor. Additionally, the single signalfrom the controller can comprise a second coded control signal causingthe intermediate logic circuit to both individually address a thirdsubset of the at least one drive signal receiver electrode traces andprovide a receiver electrode trace received signal to a first output ofthe intermediate logic circuit and (2) individually address a fourthsubset of the at least one drive signal receiver electrode traces andconnect the respective drive signal receiver electrode trace receivedsignal to a second output of the intermediate logic circuit. The firstoutput can comprise a first input to a differential amplifier and thesecond output can comprise a second input to the differential amplifier.Additionally, in at least some configurations, the second coded controlsignal can comprise an output of a shift register set by the controller,connected to control logic routing respective individual pixel locationdrive signal receiver electrode traces to the respective first output orsecond output. The intermediate logic circuit can also comprise a logiccircuit transistor switches formed on at least one of the firstsubstrate and the third substrate. In other configurations, the logiccircuit transistor switches can comprise thin film transistors formed onthe one of the first substrate and the third substrate. Additionally,the intermediate logic circuit can comprise a thin film transistoramplifier formed on one of the first substrate and the third substrateintermediate a respective drive signal receiver pixel location receiverelectrode trace and the intermediate logic circuit.

A biometric imager is disclosed which may comprise a plurality of sensorelement traces formed in or on a sensor substrate which may comprise atleast a portion of a display screen defining a biometric sensing areaand forming in-active pixel locations; an auxiliary active circuitformed in or on the sensor substrate on the periphery of the biometricsensing area and in direct or indirect electrical contact with each ofthe plurality of sensor element traces; and the auxiliary active circuitproviding a signal processing interface between the plurality of sensorelement traces and a remotely located controller integrated circuit. Theplurality of sensor element traces may form a portion of a onedimensional linear capacitive gap biometric imaging sensor. Theplurality of sensor element traces may form the rows and columns ofpixel locations in a two dimensional grid array capacitive gap biometricimaging sensor. The auxiliary circuit may comprise a pixel locationselection circuit or a pixel signal amplification circuit. The auxiliarycircuit may be mounted on a surface of the display screen. The auxiliarycircuit may further comprise a separate pixel location selectioncontroller circuit.

Biometric sensors are disclosed. Sensors can be incorporated into avariety of packages, housings and form factors. Additionally disclosedare methods of making sensors. Additionally, biometric sensorsincorporatable into a glass touch screen having an upper surface withresin which allows the signal to pass between a user's finger and asensor without compromising the signal.

Also disclosed are devices and methods that use high dielectric constantmaterials that can be mixed with molding resins to boost sensor signal.A signal boosting structure (“SBS”), residing on top of the sensor, canbe constructed from the modified resins after the mixing is completed inorder to provide mechanical durability without lowering the sensorsignal level. It was also found that the noise is less when a certaintype of mixed resin is used, resulting in an increase in Signal-to-NoiseRatio (“SNR”).

Prior solutions have attempted to increase the maximum allowablethickness of any materials that would come between the sensor and thefinger, and 0.07 mm thick glass with approximately 0.01 mm of adhesiveor 0.03 mm to 0.04 mm of decorative color coating are recognized astypical topping structures showing acceptable sensor signal levels. Withthe use of high dielectric constant materials as disclosed herein, thesignal boosting structure can be made more thick, e.g., 0.1 mm or evengreater.

It will be understood that a biometric object sensor button arrangementcore and method of forming the same is disclosed which may comprise aflex material layer; a sensor controller IC mounted on one side of theflex material layer; a metallization layer comprising a plurality ofsensor sensing element traces and controller IC input/output tracesformed on at least one side of the flex material layer, each inelectrical connection with controller IC; an encapsulation layerencapsulating the controller IC to one of the flex material layer andthe metallization layer; and a protective layer covering one of the flexmaterial layer and the metallization layer on a surface opposite fromwhere the controller IC is mounted, comprising a dielectric materialdispersed with at least one high dielectric material utilizing adispersant. The biometric object sensor button may further comprise afingerprint sensor button. The metallization layer may comprise a firstmetallization layer formed on a first surface of the flex materialcomprising the sensor sensing element traces and a second metallizationlayer formed on a second surface of the flex layer opposing the firstsurface of the flex layer and comprising at least some of the controllerIC input output traces. The button arrangement core may further comprisean extension of the flex layer and the metallization layer extendingfrom the encapsulation layer and a further encapsulation of theextension of the flex layer from the button arrangement core and theextension of the metallization layer from the button arrangement core toform a button arrangement package. A further encapsulation of theextension of the flex layer and a further deposition of dielectricmaterial on the metallization layer may be included to form a buttonarrangement package. The button arrangement core may further comprise anadhesive layer covering the one of the flex layer and the metallizationlayer and the extension of the encapsulation of the flex layer and themetallization layer; and a layer of dielectric material adhered to theadhesive layer, which may be corundum and may be deposited by thin filmdeposition or as a thin crystalline sheet(s). The method may compriseforming a flex material layer; mounting a sensor controller IC on oneside of the flex material layer; forming a metallization layercomprising a plurality of sensor sensing element traces and controllerIC input/output traces formed on at least one side of the flex materiallayer, each in electrical connection with controller IC; encapsulatingthe controller IC in an encapsulation layer formed on one of the flexmaterial layer and the metallization layer; and forming a protectivelayer covering one of the flex material layer and the metallizationlayer on a surface opposite from where the controller IC is mounted,comprising a dielectric material dispersed with at least one highdielectric material utilizing a dispersant.

INCORPORATION-BY-REFERENCE

All publications, patents, and patent applications mentioned in thisspecification are herein incorporated by reference to the same extent asif each individual publication, patent, or patent application wasspecifically and individually indicated to be incorporated by reference,for all purposes, including the specification, figures and claims as ifthe entire patent or publication was reproduced entirely herein.

BRIEF DESCRIPTION OF THE DRAWINGS

The claimed subject matter is now described with reference to thedrawings, wherein like reference numerals are used to refer to likeelements throughout. In the following description, for purposes ofexplanation, numerous specific details are set forth in order to providea thorough understanding of the claimed subject matter. It will also beunderstood that the elements disclosed and illustrated in the drawingfigures are described in a positional and relational sense in thepresent application, e.g., as “top” and “bottom,” “front” and “rear,”“left” and “right” in such nomenclature selected purely arbitrarily andin conformance with the illustrated relationships in the drawing figuresand are not intended to delimit any such orientation of the subjectmatter disclosed when in actual use, or to so limit the appended claims.It will also be evident, however, that the claimed subject matter may bepracticed without these specific details. In some instances, well-knownstructures and devices are shown in block diagram form in order tofacilitate describing the claimed subject matter.

The novel features of the invention are set forth with particularity inthe appended claims. A better understanding of the features andadvantages of the present invention will be obtained by reference to thefollowing detailed description that sets forth illustrative embodiments,in which the principles of the invention are utilized, and theaccompanying drawings of which:

FIG. 1 shows schematically components of a portion of a biometric sensorarrangement, such as a 2D grid array fingerprint sensor transmitterdrive circuit according to aspects of the disclosed subject matter;

FIGS. 2A-B schematically show components of a portion of a biometricsensor arrangement, such as a 2D grid array fingerprint sensor receivercircuit according to aspects of the disclosed subject matter;

FIG. 3 shows a simplified schematic form of a portion of a 2Dfingerprint sensor grid array, such as a portion of an X-Y sensor gridaccording to aspects of the disclosed subject matter;

FIGS. 4A-B illustrate schematic views of a drive circuit for use with afingerprint sensor grid array such as shown in FIG. 3, according toaspects of the disclosed subject matter;

FIG. 5 illustrates partly schematically, an arrangement of a biometricsensor 2D sensor formed on a substrate with a controller IC mounted inthe same substrate and intermediate circuitry also formed on thesubstrate or on a layer formed on the substrate, according to aspects ofthe disclosed subject matter;

FIG. 6 shows partly schematically a biometric imaging sensor formed by a2D grid array of capacitive gap in-active pixel location sensor elementsformed on a dielectric substrate according to aspects of embodiments ofthe disclosed subject matter;

FIG. 7 shows a partial schematic of a biometric sensor;

FIG. 8 shows part of a schematic of a second configuration of abiometric sensor wherein a molding or filling compound seals the IC andthe sides of the glass top plate;

FIG. 9 shows a simplified schematic showing an X-Y sensor array blockconnecting to an IC;

FIG. 10 shows a cross-sectional view of a compact construction for a 2Dswipe or placement grid array fingerprint sensor;

FIG. 11 shows an example of a metal layout for a sensor;

FIGS. 12A-B show transmitter or received electrode traces;

FIGS. 13A-B shows cross-sectional schematic view of sensors;

FIGS. 14A-C shows a more detailed view of transmitter electrodes/tracesand received electrode/trades formed on a substrate and fabricationstructure;

FIG. 15 shows a manufacturing process for mass producing buttonconstructions;

FIG. 16 illustrates a cross-sectional schematic view of a sensorelectrode/trace arrangement;

FIG. 17 illustrates components inside a form factor, such as a button;

FIG. 18 illustrates a laminated copper foil with silver jumpers for a 2Dsensor;

FIGS. 19A-B illustrate a chip on glass (COG) package;

FIG. 20 illustrates an example of an electrode connected to glass bywire bonding pads;

FIG. 21 is a side view of a housing with a chip positioned therein and acoating on top;

FIG. 22 illustrates a top view of a sensor and chip configuration;

FIG. 23 is a side view of a housing with a chip wherein the top coatingfits within a cavity;

FIG. 24 is a side view of a housing with a chip wherein a thin disk orplate is attached;

FIG. 25 is a side view of a sensor reel with a chip with the copper sidedown;

FIG. 26 is a side view of a sensor reel with a chip away from a sensor;

FIG. 27 is a side view illustrating the use of a coating or printing ofmixed liquid resin after the button has been built similarly to FIG. 23;and

FIGS. 28-1-28-3 show a table of results of testing with varyingdielectric materials with or without high dielectric materialdispersants.

DETAILED DESCRIPTION

The following description and the annexed drawings set forth in detailcertain illustrative aspects of the claimed subject matter. Theseaspects are indicative, however, of but one or more of the various waysin which the principles of the claimed subject matter may be employedand the claimed subject matter is intended to include all such aspectsand their equivalents. Other advantages and novel features of theclaimed subject matter will become apparent from the following detaileddescription of the claimed subject matter when considered in conjunctionwith the drawings.

According to aspects of embodiments of the disclosed subject matter,lower complexity and therefore, generally speaking, lower costtransistors, including TFT transistors made with lower cost TFTtechnologies, may be used with the sensor array to perform individualpixel signal processing or at least selection and control outside of thepixel array.

According to aspects of the disclosed subject matter a larger sensingsignal may be obtained, e.g., by increasing the signal that is coupledfrom the transmitter pixel to the finger. This can provide, e.g., analternative to the multiple receiver approach described above. Whenincorporating the appropriate logic circuitry in the transmitter linedriver circuits that operate on much larger signals that the receivercircuits, the demands on the transmitters (rows in one embodiment)multiplexing circuits can be far less stringent than for multiplexingthat is done on the receiver lines, e.g., because they are carrying muchsmaller signals. Providing in-pixel amplification circuitry can reducethe demands on the receiver circuitry considerably. However, in-pixelamplification, as noted above, can be costly and use a good deal ofpixel real estate to implement and the amplification may itself be ofrelatively low performance, e.g., noisy and lacking in much gain.

According to aspects of embodiments of the disclosed subject matter asensor pixel array may be fabricated which does not require any TFTcircuitry in the array itself, i.e., at the respective pixel locations,or at least no higher performance TFTs. The extra processing cost offabricating such higher cost TFT circuitry on the glass can effectivelybe removed from the fabrication process over the majority or all of theof the array substrate. In addition to controlling which transmitterlines and/or pixels are activated simultaneously, it may be advantageousto activate certain transmitters or combinations of transmitters,including doing so at different voltages to achieve an improvedfingerprint image from the receiver circuits. A best available oroptimized combination of signals achieving the desired signal strength(e.g., reducing the noise in the fingerprint image) and fingerprintimage resolution, e.g., number of rows and columns may be empiricallyand/or dynamically determined and utilized. In much the same manner thatmultiple transmitter/receiver lines can be activated simultaneously toincrease the signal strength in a 1D linear sensor element array,multiple receiver lines can also be tied together, e.g., in the readoutmultiplexer circuit to increase the strength of the signal that ispassed on to the receiver line(s) sense amplifier.

Activating multiple transmitter pixels in a two-dimensional fingerprintsensor pixel array can be accomplished in several forms. Fortwo-dimensional sensor arrays, as an example, which are operated in apassive mode, e.g., including no active (such as, TFT) circuitry at eachpixel, this can be accomplished in its simplest form by activating morethan one transmitter line at a time. As is known, if the transmittersignals are all generated in a single controller integrated circuit(“IC”), or cooperating controller IC, the IC(s) may contain logiccircuitry to activate multiple transmitters in specific patternssimultaneously in a fashion similar to the one-dimensional sensor casereferenced above.

Alternatively, and according to aspects of embodiments of the disclosedsubject matter, the transmitter signals can pass to the sensor arrayelectrodes, e.g., in a sensor array finger sensing area, e.g., through asecondary circuit residing on the same substrate as the sensor arrayelectrodes (which may be a silicon wafer, glass sheet, plastic sheet, orany other dielectric-coated substrate). This can be, e.g., in the formof multiplexer circuitry formed, e.g., of TFTs formed in or on the arraysubstrate or in an added layer, such as a polysilicon layer on theglass, flex, or the like substrate for the sensor array traces, and canbe of simple logic design, e.g., requiring fewer or no polycrystallinesilicon devices and/or larger device sizes or at least less highperformance devices than would be required to implement pixelselection/multiplexing and/or amplification at the pixel cell level.Logic circuitry can be added to the transmitter line multiplexers thatprecede the analog line driver circuits. In this case specificcombinations of outputs from the primary shift register in thetransmitter multiplexer may be combined to activate specific patterns oftransmitter line drivers, or the shift register itself may be modifiedto produce a different pattern of output signals.

A 2D touch sensor and/chip on glass arrangement along with certainpackaging techniques can be beneficial for applications of biometric,e.g., fingerprint sensors for use in authentication applications such ason small user electronic devices, e.g., portable cell phone, iPad®,tablets, personal digital assistants, such as Blackberry® mobiledevices, etc. According to aspects of embodiments of the disclosedsubject matter, the use of mold plastic around the edge of the glass,e.g., in a button configuration, such as may utilize the same glass as asurrounding display screen, such as a touch screen, into which thebutton may be inserted in an opening in the display screen,advantageously having the same glass and thus the same or relatively thesame coefficient of thermal expansion (“CTE”). Electrical connectionsmay be brought out on the side or the back (“underside”) of the button,with the glass exposed on the top side.

There may be several options for electrical connections as described inconnection with the figures below. In one example, a printed circuitboard (“PCB”) type design, utilizing, e.g., a small outline package(“SOP”) or small outline integrated circuit (“SOIC”) surface mounted IC,can be bonded to, or inserted into an opening in a glass substrate,which substrate may be the same piece of glass that forms a 2D touchscreen and to protective covering for biometric sensor elements/traces,e.g., a 1D or 2D sensor array and which may also include a sensorcontroller integrated circuit (“IC”). A molded enclosure utilizingsuitable materials, such as epoxies or plastics may be formed with theglass exposed on one side. This invention can extend to, for example,use in a shrink small outline package (“SSOP”), such as may employ “gullwing leads”, quarter-size small outline package surface mount packaging(“QSOP”), thin small outline packages (“TSOP”), thin shrink smalloutline packages (“TSSOP”), etc., as an example, with glass as a topsurface.

For a system in a package (“SIP”) embodiment according to aspects of thedisclosed subject matter passive components can be added on the PCB, andcomplete the construction. According to aspects of the disclosed subjectmatter chip on glass (“COG”) package concepts may also be applied, e.g.,to supplement 2D sensor on glass, or stand on separate embodiments of,e.g., chip on glass packaged embodiments.

Turning to FIG. 1, as an example, one straightforward implementation forsuch a sensor array can be to place an array of OR gates , , , betweenthe outputs of a shift register 30 and the line driver transistors , , ,as shown in the partial row driver circuit depicted in FIGS. 2A-B. Theoutputs of the OR gates , , , control the transistors , , , to place thetransmit signal on the respective transmit line(s) Tx_(n−2), Tx_(n−1),Tx_(n), Tx_(n+1), and . This can be done according to the content of theshift register 30 output on each of the outputs, , , , of the shiftregister in each clock period according to the coded content of the bitsshifting through the shift register. As an example, if the content ofthe shift register 30 from top to bottom as shown in FIG. 1, and thusthe outputs on , , , and , , , were 0, 1, 1, 0, 0 . . . , then thetransmitter lines Tx_(n−2), Tx_(n−1) and Tx_(n) would be activated,since the inputs, to OR gate would be 0, 1, the inputs , to OR gatewould be 1, 1, and the inputs , to OR gate would be 1, 0. The outputs ofthe OR gates , and would control the selection transistors, and to placethe transmit signal on the transmit lines Tx_(n−2), Tx_(n−1) and Tx_(n).Similarly, adjacent transmitter lines Tx_(n) and Tx_(n−1) could beactivated with a bit pattern of 0, 0, 1, 0, 0, resulting in the outputsof the OR gates and connecting transmit lines Tx_(n) and Tx_(n−1) to thetransmit signal.

It will also be understood by those skilled in the art, that the circuitof FIG. 1 is merely an example and the 2D sensor arrayselection/activation/multiplexing circuitry could be fabricated to coverall transmit circuit lines, e.g., all rows of the array or largernumbers of rows, but less than all rows, forming separate sections ofrows of the 2D sensor array. Similarly the shift register(s) couldcontain various bit encoding patterns such as to activate more than twoadjacent transmit lines, or transmit lines separated by non-activatedtransmit lines, etc. The same or different patterns of activation may beimplemented in each section of transmit lines controlled by a separateshift register.

Multiple receiver lines , , , can be enabled with a circuit , as seen inFIG. 2, that is very similar to the one depicted above. In such case theline driver transistors , , , can be replaced by pass transistors , , ,that simply pass any combination of analog signals from the selectedreceiver lines Rx_(n−2), Rx_(n−1), Rx_(n), Rx_(n+1) , , , and to thereceiver's main sense amplifier(s) under the control of the OR gates, ,, , based on the outputs , , , and from the shift register.

The above discussion utilizes convention that transmitter signals aresent on the row lines Tx_(n−2), Tx_(n−1), Tx_(n), Tx_(n+1) as seen inFIG. 1 and received signals are received/read out on the column linesRx_(n−2) Rx_(n−1), Rx_(n), Rx_(n+1), as seen in FIG. 2A, although theselection circuitry , could be built with the opposite orientation.Also, according to aspects of embodiments of the disclosed subjectmatter, if the two-dimensional sensor grid array as seen in FIG. 5,interfacing with the selection circuitry 10 also is active circuitry,e.g., contains active (such as, semiconductor) elements within eachpixel (not shown), e.g., to implement full active matrix operation,additional logic may be placed within a pixel cell to achieve specificpatterns of activated transmitter/receiver pixels. If one or moreadditional (perhaps logic-level) input row or column signals areprovided in the array, logic circuits in adjacent pixels can allowspecific transmitter pixels near a central target pixel to be activatedwithout activating an entire row's transmitters. While such an approachmight increase the sensor readout frame rate, optimal combinations ofactive and inactive transmitter pixels may be found to improve thesignal levels and therefore the overall fingerprint imaging done by thefingerprint image sensor.

According to aspects of the disclosed subject matter, such sensor arrayscan result in significant reductions in cost. Multiplexing thetransmitter and/or receiver lines on an auxiliary circuit, e.g., oneimplemented at or near the sensor array, such as on the same substrateor at least a layer deposited on the same substrate, such as apolysilicon layer in which the TFT transistors of the auxiliary circuitcan be fabricated, can eliminate a large fraction of the I/O connectionson the controller IC as well as circuitry on the real estate of thecontroller IC (not shown). This can allow a smaller, coarser, morereliable and less expensive IC and a coarser and more reliableIC-to-substrate attach process to be used. In addition, the die size andcost may also be reduced because IC size and cost is also driven by thenumber of required I/O pads.

According to aspects of embodiments of the disclosed subject matter,attempts to reduce the noise levels in a two-dimensional fingerprintsensor array are proposed which, e.g., compare each pixel's signal to anaverage signal level across another portion or portions of the 2D sensorarray. Time dependent, and to some extent spatially dependent, noisethat affects many pixels in close proximity in such an arraysimultaneously can be mitigated, according to aspects of the disclosedsubject matter. This may be done, e.g., by effectively subtracting thenoise which is obtained by averaging signals from other pixel locations,e.g., the pixels surrounding a target pixel, from the signal of thetarget pixel. Other pixels may also be selected, e.g., by empiricaland/or dynamic testing to determine pixels whose signals, when selected,will most effectively, most often, most simply, etc. serve to remove theundesired noise from the pixel signal being sampled at the time.

According to aspects of the disclosed subject matter, an average noisesignal obtained from multiple nearby sensor-to-finger capacitancereadings positioned in relation to the target pixel's sensor-to-fingercapacitance location, e.g., at a transmitter trace/receiver tracecrossover point, can be subtracted from the target pixel receivedsignal. This type of averaged noise subtraction can be more effective atcompensating for noise and other sources of error, e.g., that mightarise from sources outside the plane/area of the sensor, for example, onthe surface of the finger or on the surface of the sensor's protectivecoating, etc. As an example, for passively addressed 2D sensor array, asseen in FIG. 3, the average signal for all the pixels in an active rowexcept the target pixel can be obtained by tying together all the othersignal lines from the inactive columns, as opposed to the active column,as illustrated in FIG. 3.

A possible shortcoming of existing solutions for accounting for theadded capacitance, including parasitic capacitances, due, e.g., toselecting from multiple sensor pixel element locations for activation astransmitter locations and activation as receiver locations is that thereceive lines from the selected receiver pixel locations may,individually or collectively or both, be loaded down with lots ofbackground capacitance. This can reduces their sensitivity and/or makethe received signal smaller. Sources of background capacitance mayinclude: capacitance between the receiver lines to surrounding metal(like the adjacent or surrounding transmitters or receivers); thecapacitance of the switches that multiplex the receivers to a centralreceiver line; the capacitance of the connection to the ASIC, e.g., atthe interconnection bumps and bond pads of the ASIC; the capacitance ofthe ESD protection structures (i.e., diodes), e.g., under the bond padsof the controller chip and the capacitance of the sensing amplifier onthe controller chip. the transmitter state machine

Addressing the first item, i.e., the capacitance coupling to thesurrounding metal, is beyond the scope of the specific correctionsaddressed in this application. The other four may be mitigated, e.g., byadding an amplifier or buffer built to the signal output line(s). Such abuffer of amplifier, according to aspects of the disclosed subjectmatter may be formed on the same substrate as the sensor transmitter andreceiver electrode traces of a separate substrate attached to thatsubstrate. This may be done, e.g., utilizing active devices formed onsuch substrate, e.g., thin-film-transistor (“TFT”) devices on a glasssubstrate, e.g., between the receiver lines and the rest of thebackground capacitance.

Turning to FIG. 2B, a modified version of the circuitry shown in FIG. 2Ais presented. Many sources of background/parasitic capacitance areshown. For example, in a given case, such as, the selection of R_(xn)156 as the receiver electrode trace to be connected to the main receiversense amplifier line 160 adds capacitance (not shown) to the R_(xn) line156 at the input side of the switch 146. The output side of switch 146also adds capacitance. Additionally, on the output side of the switch146, even though all the other switches 142,144, 148 might be turnedoff, they are still connected to the main receiver sense amplifier line160 and add capacitance to it. The routing of the main receiver senseamplifier line 160 near other conductors (other metal lines, vias, etc.,not shown) adds additional capacitance to the main receiver senseamplifier line 160. The metal-to-metal capacitance due to the routing ofthe main receiver sense amplifier line 160 as well as the capacitancefrom the switches 142, 144, 146, 148, for illustration purposes arelumped into a single symbolic capacitance.

At the boundary to the controller IC, e.g., an ASIC 908, a bond pad 820on the ASIC 908 can add significant additional capacitance. Under thisbond pad 820 inside the ASIC 900 can be ESD protection circuits, shownsymbolically as diodes 830 and 831. The sensing amplifier 840 can alsoadd capacitance. All of these ASIC capacitances, for purposes ofillustration are lumped into a single symbolic controller ASICcapacitance 850.

According to aspects of the disclosed subject matter reduction in theeffect of these capacitances 820 can be achieved. For example,metal-to-metal routing may be carefully controlled, and sometimes thebackground capacitance can be reduced by eliminating or reducing theshielding around the main receiver sense amplifier line 160. Althoughthis can reduce the background capacitance and thereby increase thesensitivity of the main receiver sense amplifier line 160, it can alsoincrease the susceptibility to external noise sources which mightotherwise have been blocked by the shielding.

Another approach may be to reduce the background capacitance, e.g., byreducing the size of the switches, as an example, switches 142, 144,146, and 148. However, doing so can also increase the resistance of theswitches 142, 144, 146 and 148, which can substantially reduce themagnitude of the received signal on the receiver sense amplifier line160. Still another way to reduce the background capacitance can be, asan example, to reduce the size of the ESD protection circuits 830, 831.This can, however, have an undesired effect of increasing thesusceptibility of damage due to an ESD strike.

Current packaging and mounting technology, e.g., for biometric objectimage sensing devices, such as are sold by the assignee of the presentapplication, e.g., where the receiver lines, such as, 152, 154, 156, and158 are created in metal on a ball grid array (“BGA”) or chip on flex(“COF”) substrate, the methods to reduce background capacitancedescribed above may be the only alternatives, e.g., resulting inincreased noise, increase ESD susceptibility, etc). BGA and COFtechnologies can block or at least limit any ability to put activedevices (e.g., transistors) on the substrate, e.g., next to the receiverlines 152, 154, 156, and 158.

However, if the sensor array, e.g., 200 in FIG. 3 with, e.g., receiverelectrode traces 152, 154, 156, and 158 is implemented on a glasssubstrate, then it is possible to use TFT's to add active devices nextto the sensing array, e.g., at the interface between the sensor array200 receiver electrode traces, e.g., 152, 154, 156 and 158, and thecontroller IC 900. This can, among other things, allow for the inclusionof sampling and/or amplifying circuits, e.g., amplifiers, unity gainamplifiers, or buffers 801, 802,803, 804 between the receiver electrodetrace lines 152,154, 156, and 158 and the background capacitance 810,850described earlier.

The choice of whether to implement amplifiers, unity gain amplifiers, orbuffers at locations 801, 802, 803, and 804 can depend on the quality ofthe TFTs that can be constructed on the available substrate, e.g.,crystalline silicon, poly-crystalline silicon, amorphous silicon, glass(non-crystalline), etc., the physical size of the constructed TFTs, andthe proximity of the TFTs to the sensor array, among other things.optimizations of these factors for the specifications for thecontemplated TFT's will be well within the skill of the art, withoutundue experimentations, but have not been studied by applicants as yetnor has the precise TFT capability(ies) needed, The advantages ofaspects of the disclosed subject matter can, however, be understood bythose skilled in the art without the specifics of these TFT details. Forcurrent purposes, the elements 801, 802, 803, and 804 as unityamplifiers, otherwise known as buffers, which could consist of, e.g., asingle TFT transistor in a source-follower configuration. The advantagebeing, in part, the TFT is more rugged than an amplifier on an ASIC IC,capable of handling a higher voltage, built on a cheaper substrate thana crystalline silicon wafer substrate, e.g., by deposition technologiestypically used for, e.g., printed circuit boards (“PCB's”), etc. On theother hand, an amplifier constructed, e.g., on a crystalline siliconsubstrate may have better amplification gain control, larger dynamicrange, less noise, etc.

Whatever is the case, adding buffers 801, 802, 803, and 804 between thereceivers 152, 154, 156, and 158 and the rest of the backgroundcapacitance 810, 850, provides for the receiver electrode traces 152,154, 156, and 158 to be loaded only by the input capacitance of therespective buffers 801, 802, 803, and 804 and not the backgroundcapacitance 810, 850 of the rest of the system. This can, e.g.,substantially increase the sensitivity of the receivers 152, 154, 156,and 158. The buffers 801, 802, 803, and 804 drive the backgroundcapacitance of the rest of the system.

In such a case, active column 250, Cn, contains the active pixel 220being read, and the signals from all other pixels 212 in the active row210, i.e., from inactive columns 230, C₁ through C_(n−1) and C_(n+1)through C_(m), can be combined to obtain an average 270 that can, e.g.,be subtracted from the active pixel 220 signal, output 280, on thecolumn C_(n) output line to reduce the noise components in the signaloutput from the active column 250, C_(n). The connections that tietogether all the average background signal on the column lines C₁through C_(n−1) and C_(n+1) through C_(m) can be implemented in TFTcircuitry on the sensor array 200 substrate that is part of, orprecedes, the column readout multiplexer/shift register circuitry, asseen in FIG. 4.

In FIG. 4A there can be seen an example of a selector circuit 300,including a selection logic circuit, such as shift register 330. As eachshift register output signal, SR_(n−1), SR_(n), SR_(n+1), SR_(n+2) . . ., 332, 334, 336, 338 . . . , is enabled in sequence, as an example, allof the other shift register outputs SR_(n−1), SR_(n), SR_(n+1), SR_(n+2). . . , 332, 334,336, 338, can be set low. The enabling (e.g., settingto 1) of each respective SR_(n−1), SR_(n), SR_(n+2) . . . , 332,334,336, 338, . . . , activates the respective one of the receivertraces Rx_(n−1), Rx_(n), RX_(n+1), RX_(n+2) . . . , of each respectiveindividual active column 250 from among the columns C_(n−1), C_(n),C_(n+1), C_(m). As an example, as shown in FIG. 3, C_(n) is active whileC_(n−1), C_(n+1), C_(m) . . . , are inactive. As an individual columnline SR_(n) is enabled, corresponding to column C_(n) in FIG. 3, thereceiver signal Rx_(n) is transferred to the primary output signal line380 through respective selection transistor, i.e., 324, from among theselection transistors 322, 324, 326 and 328. At the same time all theother lines Rx_(n−1), RX_(n), RX_(n+1), RX_(n+2) . . . , are connectedto the background/average signal line 360 through each respective columnselection transistor 342, 346, 348, e.g., due to the presence of theinverters 390 on the shift register 330 outputs SR_(n−1), SR_(n),SR_(n+1), SR_(n+2) . . . , 332,334, 336, 338. Additional logic may beincorporated in addition to, or replacing, the selector circuit 300,e.g., to tie specific patterns of receiver line signals to either orboth of the primary output signal line 380 or the background/averagesignal line 360.

There may be benefits to selecting specific combinations of columnsignals to combine to obtain the average signal level, rather thancombining all the pixels in a row. For example, to reduce the impact ofnoise contributions that have a short distance scale (but larger thanthe feature sizes the sensor is reading, e.g., as determined by thepitch of the pixel locations in the rows and columns), it may bebeneficial to combine the signal from one or several column readoutlines adjacent to the target pixel's readout line, either on one sideonly or on both sides. In other cases it may be preferable to combineonly the signals from pixels that are relatively far from the targetpixel (more than several pixels (rows or columns) away, for example,such a sensor according to aspects of the disclosed subject matter mayresult in improved sensitivity, e.g., compared to other passive arrayfingerprint sensors, e.g., 1D or 2D, and possibly lower cost than activematrix fingerprint sensors, for reasons explained above.

According to aspects of embodiments of the disclosed subject matter,there may be employed certain methods of incorporating sensor 10 readoutcircuitry, e.g., along with sensor elements/traces and a controllerintegrated circuit (“IC”). This concept is extended here totwo-dimensional sensors, where the target pixel is the equivalent of anFI line, as discussed in co-pending U.S. Patent Pub US 2013/0177220 A1to Erhart, discussed above, and the equivalent of the NI signal isactually an average of multiple pixels near the target pixel (orthroughout the entire 2D array).

According to aspects of embodiments of the disclosed subject matter thenumber of signal lines that must be routed to the rows and columns of afingerprint sensor array having a two-dimensional matrix format throughthe low performance TFT circuitry on the periphery of the sensor sensingelement array can be significantly reduced. The row and columnmultiplexing, drive and readout circuits can be, e.g., fabricated on aseparate glass sheet, e.g., using relatively low performance TFTtechnology, and can then be bonded as long thin strips along theperiphery of the sensor pixel array. This can effectively replace thesilicon IC with an IC made on glass, e.g., semiconductor-on-glass, e.g.,incorporating, e.g., relatively low performance TFT circuitry, or whichis otherwise much less expensive per area than, e.g., fabricating an ICon a silicon substrate using integrated circuit mask workphotolithography fabrication processing.

Building the relatively lower performance and more cost effective TFTmultiplexing circuitry on a glass substrate that is similar to theprimary array's glass substrate, so that both the array glass andmultiplexer strip glass have the same or similar coefficients of thermalexpansion (CTE), also can simplify the silicon-on-glass IC attachprocess by eliminating CTE mismatch stresses between the array areaglass and the glass substrate of a multiplexing circuit, e.g., aseparate IC. The attach process can further be simplified by matchingthe electrode (trace) pitch of the TFT silicon-on-glass circuitry to therow and column pitch of the sensor pixel array electrodes/traces, whichmay be coarser than would be expected for an entire integrated circuitmade with IC made with semiconductor-on-glass technologies. A glassmultiplexer circuit, e.g., made with TFTs, could be thinned prior tobeing attached to the array sensor electrode/traces, or it could befabricated on thin (0.025-0.250 mm) glass initially, either in flexibleform or while temporarily adhered to a carrier sheet, or otherwise, tofacilitate processing.

According to aspects of embodiments of the disclosed subject matter,advantages of this form of construction for the sensor array traces andperiphery circuitry, can be, e.g., for a 2D array matrix formatfingerprint sensor that does not require any or at least any highperformance TFT circuitry at each pixel, added row and column circuitry,such as row and column multiplexer circuitry, that can easily and atlittle added cost, be added to the glass substrate, dramaticallyreducing the number of signal lines along the ultimate periphery of thesensor pixel array, while avoiding the cost of a TFT process for theentire sensor pixel array area.

Should the primary sensor pixel array need to incorporate active TFTcircuitry, if this circuitry can be implemented with a TFT process thatis significantly less expensive than a higher performance TFT process,which may be required for the row and/or column multiplexer circuits,such a method could still be used to allow the sensor pixel array to befabricated at a lower cost (for example amorphous silicon or metal oxideTFTs), while attaching the higher performance TFT multiplexer ICs to theperipheral circuitry to provide the required higher performance TFTsonly where they are needed. Such can reduce the overall cost of thefingerprint image sensing device. Using a glass substrate for themultiplexer IC fabrication also, e.g., allows the CTE of the multiplexerIC to be matched to the CTE of the fingerprint pixel sensor array sensorelements, permitting more flexibility and a wider process window for theattachment process.

Turning now to FIG. 4B, according to aspects of embodiments of thedisclosed subject matter, the just discussed advantages can be achievedalso with circuitry containing “double throw” switches, such as switches322 and 342 in combination and 334 and 344 in combination, 326 and 346in combination and 328 and 348 in combination. Such “double-throw”switches, e.g., according to the signal present in the shift register330, supplied by the ASIC controller 900 can connect a respectivereceiver electrode trace R_(xn−1), R_(xn), R_(xn+1), and R_(xn+2), etc.to one or the other of the sense amplifier line 360 or 380. In thatregard, the overall content of the shift register 330 could beconsidered a “single signal” from the controller, i.e., one signalcontrolling a plurality of single throw switches in the case, e.g., ofFIG. 2B, and a plurality double throw switches in the case of FIG. 4B,or the individual shift register positions could be consider a “singlesignal” from the controller, controlling one single throw switch (e.g.,FIG. 2B) or one double throw switch (e.g., FIG. 4B).

In FIG. 4B both main receiver sense amplifier lines 360, 380 can havetheir own set of background capacitances. Only one set of buffers 801,802, 803, 804 would be necessary to drive both respective switches 322and 342 in combination, 334 and 344 in combination, 326 and 346 incombination and 328 and 348 in combination, in the “double throw”configuration and any background capacitance 810, 850 on the other sideof the switches 322 and 342 in combination, 334 and 344 in combination,326 and 346 in combination and 328 and 348 in combination.

Each sense amplifier line 360, 380 can have its own separate ASICamplifier 840, the output of one being connected to, e.g., a first inputto a differential amplifier and the output of the other being connectedto, e.g., a second input to the differential amplifier, e.g., for noisereduction. It will be understood by those of ordinary skill in the artthat, e.g., depending on the number of receiver electrode traces usedfor noise reduction that are connected to the amplifier 840 on the senseamplifier line 380, as compared to, e.g., only one or so connected tothe amplifier 840 on the sense amplifier line 360, there may have to bean adjustment to the output of the respective amplifier(s) so as not tooverload one input to the ultimate differential amplifier (not shown)with respect to the other. This may be done by, e.g., preselecting anumber of receiver electrode traces to be connected to each of outputsense amplifier line 360 and 380 and selecting the gain of the amplifier840 on line 360 with respect to the gain of the amplifier 840 on line380. This could also be done dynamically as will be understood by thoseskilled in the art by dynamic gain adjustment circuitry (not shown)based upon the relative numbers of receiver electrode traces connectedto each amplifier 840, i.e., connected to each respective senseamplifier line 360, 380. Other means of accomplishing this balancingcould be done, e.g., without using a differential amplifier at all,e.g., digital to analog conversion circuitry (not shown) could beconnected to the outputs of the respective amplifiers 840 on lines 360and 380, and determining the output of the ASIC could be done digitally,including the necessary balancing.

It will be understood by those skilled in the art that the presentapplication discloses a biometric (fingerprint) image sensing system andmethod that can, among other things, correct or at least alleviateproblems associated with addressing hundreds or even thousands of sensorelement electrode traces, e.g., in a 1D passive capacitive gap sensorarray or a 2D passive capacitive gap sensor array, or subsets of suchsensor element electrode traces. This may be done, e.g., by usingintermediate circuitry, e.g., logic circuitry, disposed between theindividual sensor element electrodes traces and an IC controllercontrolling the biometric image sensor which is configured to, based ona “single” command from the IC, individually address a first subset ofelectrodes to receive a resulting signal and individually address asecond subset of electrodes to receive a noise metric signal, each usedin a differential measurement with the resulting final output signalcomprising an output of the biometric image sensor.

The biometric (fingerprint) image sensor may comprise a processingsystem configured to sense the biometric (fingerprint) image atbiometric image pixel locations within an array of pixel locations andprovide sensor output signals for a controller doing the processing torecreate the biometric (fingerprint) image from the pixel locationoutput signals. The biometric image sensor may comprise a plurality ofsensor elements formed by sensor element electrode traces configured tocapacitively couple a drive signal applied to an input object (finger)at an image pixel location and received, after being capacitivelyaltered by passing through the biometric object (finger), on a drivesignal receiver electrode trace for the respective pixel location.

According to aspects of the disclosed subject matter, intermediate logiccircuitry can be utilized to couple to the processing system (e.g.,controller ASIC integrated circuit) and the sensor element pixel elementtraces. The intermediate logic circuitry, e.g., can be configured tocouple at least one sensor element electrode trace(s) to a first inputof a differential amplifier in the ASIC, and couple another sensorelement electrode trace(s) to a second input of the differentialamplifier in the ASIC. The processing system ASIC may be configured toswitch the intermediate logic to couple a different second sensorelement electrode trace(s) to the first differential amplifier input andcouple the another sensor element electrode trace(s) to the second inputof the differential amplifier based on a single control signal sent fromthe ASIC to the control logic, e.g., forming a multiplexer (“MUX”) inthe intermediate logic circuitry.

According to additional aspects of the disclosed subject matter, byutilizing thin film transistor (“TFT”) logic to control the timing ofthe transmitters, a split transmitter state machine may be created,i.e., wherein half of the transmitter state machine is on the ASICintegrated circuit silicon die and half of the transmitter state machineis on the substrate containing the sensor element electrode traces (orattached to a substrate containing the sensor element electrode traces)in the form of TFT logic. As such, by way of example, an amplifier maybe formed on each pixel location drive signal transmitter line and oneach drive signal receiver line, e.g., for signal smoothing, signalboosting or the like. In addition, advantageously, one die can becreated, e.g., containing the ASIC and intended to be mount to and/or bepackaged in a different package, than contains the substrate(s)including the sensor element electrode traces. According to aspects ofembodiments of the disclosed subject matter, such ASIC can be designedand manufactured to be “highly programmable”, e.g., enabling thechanging of the transmitter drive signal lines firing timing and/ororder to accommodate connection to other ICs, circuitry, etc. in theoverall biometric imaging sensing and recreation system, e.g.,accommodating different packages and interconnections.

A buffer/unity amplifier may be coupled to respective receiver electrodetrace line(s) (e.g. in a source follower configuration) to transitionthe received modified drive signal into the ASIC, to accommodate properprocessing of such signal(s). ESD robustness can be facilitated, e.g.,by removing diodes on the AISC. By selecting the properties of the TFT'sused as the transmitter drive signal medium or receiver received drivesignal medium, or both, the level of such signals may be increased,e.g., because such TFT's external to the ASIC can have higher voltagecapability. Instead of utilizing high voltage I/O circuitry, e.g.,buffers and high voltage step downs and the like, on the ASIC silicon,according to aspects of embodiments of the disclosed subject matterlevel translator TFT's external to the ASIC can be utilized, e.g., toproduce and handle drive signals and received signals at higher voltagesthan the ASIC can handle. Higher voltages make the signal larger. It isharder to increase such signals within the ASIC.

In addition, it will be understood by those skilled in the art that byusing TFT switches to select multiple groups of receivers theintermediate logic circuitry may be utilized to, e.g., perform functionsoutside the ASIC that can benefit the capture and processing of thebiometric (fingerprint) image. As an example, the TFT's can be utilized,as disclosed in the present application to do code division multiplexing(“CDM”) encoding of the transmitter electrodes trace inputs and receivertrace output destination(s) and the like. This can, e.g., be used toaccomplish choosing which receiver electrode trace received signal goesto, e.g., the positive input of an amplifier, e.g., a differentialoutput amplifier and which receiver electrode trace received signal(s)goes to, e.g., the negative input of the differential amplifiers. Suchcode division multiplexing may be done, e.g., by simply generating acoded signal to the intermediate logic circuitry to set up themultiplexing paths according to the coded signal, e.g., contained in aregister the outputs of which control the outputs of the logiccircuitry, as noted in the present application.

It will also be noted that the sensor elements can be coupled to/adhereda sensor substrate surface using a high K material.

As can be seen in FIG. 5, a fingerprint sensor 500 may be constructed asdepicted in FIG. 5. Here the fingerprint sensor pixel sensorelectrode/tracer array 506 can contains all the row and column sensorsignal electrodes/traces (not shown), and could include lowerperformance active TFT sensor pixel circuitry (not shown), if needed,e.g., for reset, preloading, etc., but avoiding more exact and precisetransistor requirements, e.g., for amplification, individual cellselection, control, etc., i.e., multiplexing, etc. A row multiplexer 510and a column multiplexer 520, respectively, may be attached to rowoutput lines 512 from the sensor array 506 rows (not shown) and columnoutput lines 522 from the sensor array 506 columns (not shown). thesemay be TFT-on-glass ICs that are, e.g., formed on the sensor substrate502 or formed on a separate piece of glass (not shown) and bonded to thesensor substrate 502, or may even be a separately formed chip-on-glass(“COG”) multiplexor IC mounted on the sensor substrate 502, e.g., iftransparency is not an issue in the areas covered.

An optional controller IC 504, e.g., including the sensor controllercircuitry, e.g., for generating the drive signals, and timing of thedelivery of the drive signal to transmitter drive lines, and receiveramplification and timing and other input/output control and the like,can also be mounted on the sensor substrate 502. Otherwise the optionalcontroller IC 504 can simply contain some additional interface circuitryformed with the less costly TFT transistor technology may interface thefingerprint sensor 500 with a remotely housed and mounted controller IC(not shown) and may also be mounted on/bonded to the sensor substrate502 if that functionality is not already provided in the row or columnmultiplexer(s) 510, 520 or multiplexer ICs 510, 520.

The TFT multiplexer circuits 510, 520 and/or optional IC504 could befabricated on the sensor substrate 502 glass with any TFT technologythat provides the necessary TFT performance, such as low temperaturepoly silicon (“LTPS”), e.g., where transistors are formed in or on anamorphous layer of a dielectric, such as silicon dioxide (SiO₂), ormelted amorphous silicon forming a generally coarsely grainedpolysilicon layer, transparent metal oxide TFTs such as Zinc Oxide (ZnO)or Indium Gallium Zinc Oxide (IGZO), or possibly even amorphous siliconor organic TFTs. More complex circuitry and or TFT devices may be formedin, e.g., polycrystalline silicon, e.g., as may be formed by lasercrystallization of amorphous silicon to form larger or non-existentgrain boundaries, or the like processes. The TFT-on-glass ICs would bebonded to the sensor pixel array substrate 502 with conventional ICattach techniques, including conductive (anisotropic or isotropic) orinsulating adhesives, flip chip, solder ball or like processes.

It will be understood that the fingerprint sensor 500 may be formed on aglass substrate that form, e.g., a portion of a display touchscreen orof the same material as such a touchscreen and intended for insertioninto an opening formed in such a touchscreen. The array 506, with itssensor elements, multiplexers 510, 520 and optional IC 504 may be formedon/bounded to (either as separate strips of glass or other material, orseparate ICs) on the inside of the touchscreen, i.e., opposite from thesurface touched by a user. Products manufactured with the abovedescribed aspects of the disclosed subject matter can be expected tocost less than those which use high performance TFT technology, e.g.,over the entire sensor pixel array substrate 502.

Referring now to FIG. 6, a diagrammatic view of one embodiment of a 2Dgrid array sensor 600 configured according to aspects of embodiments ofthe disclosed subject matter is illustrated by way of example. In thisconfiguration, pickup/receiver electrodes/lines or top plates/traces 602may be positioned on an insulating dielectric substrate layer 604 andconfigured to transmit a signal into a surface of an object located inclose proximity to the pickup/receiver electrodes/traces 602. Drivelines or bottom electrode plates/traces 606 can be positioned juxtaposedto and substantially perpendicular to the pickup electrodes/traces 602and can be located on an opposite side of the a insulating dielectricsubstrate 604 to form a 2D grid array if pixel locations 620 at thecrossover points of the pickup electrodes/traces 602 and driveelectrodes/traces 606. The pickup electrodes/traces 602 can beconfigured to receive the transmitted electromagnetic fields, as shownin FIG. 6, modified by the impedance characteristics on an object placedwithin the range of those electric fields.

FIG. 6 further illustrates how the electromagnetic fields can extendbetween the drive electrodes 606 and the pickup electrodes 602 throughthe dielectric substrate 604. Without an object within proximity, theelectric field lines generally can be uniform within the sensorstructure and between the different electrodes 602, 606. When an objectis present, such as a finger of a user, a portion of the electric fieldlines can pass through the finger and can be absorbed by the finger anddo not return to the pickup electrodes 602.

In operation, the drive electrodes 606, can be driven by a schematicallyillustrated high frequency alternating current (or pulsed square wavevoltage source, or the like) 610, illustrating such drive electrode 606being individually activated. A drive electrode 606/pickup electrode 602pair 620 can be activated by selecting a column formed by apickup/receiver electrode 602 that is activated, i.e., connected to anoutput for processing of the signal at the pixel 620. The result is acircuit that transmits electric field from active drive plate 606 intothe combined dielectric of the insulating layer 604 and the finger (notshown) via the electric field lines in the vicinity of the crossoverpoint 620, and received by the active pickup electrode 602. Some of thefield lines can be captured by, or at least modified by, e.g., having acapacitive impedance changed by, the object when it is placed in thevicinity the active electrode pair 620. Variations in the finger, suchas peaks and valleys and other features of fingerprint on the finger,can be detected and captured electronically by capturing and recordingthe resulting electric field variations occurring at respectivecrossover locations 620 of the drive electrodes 606 and pickupelectrodes 602. Similar to common capacitance based placement sensors,the sensor can capture a type of image of the fingerprint surfaceelectronically, and generate a representation of the features andcharacteristics of the fingerprint in the fingerprint sensor exampledescribed according to aspects of embodiments of the disclosed subjectmatter.

In this configuration of FIG. 3, only one active electrode pair isillustrated. However, the embodiment is not limited to this particularconfiguration, where one single electrode pair, several electrode pairs,or even all electrode pairs may be active at one time for differenttypes of operations and signal processing to gather the individual pixeldata for the reconstruction of a fingerprint image. In practice, it maybe desirable for less than all of the electrode pairs to be active at agiven time, so that any interference that may occur between close-bypixels would be minimized. In one embodiment, a drive electrode 606 maybe activated, and the pickup electrodes 602, e.g., in a given column ofpickup electrodes 602 may be scanned one or more at a time so that acolumn or columns pixel locations can be captured along the respectivedrive electrodes and pickup electrodes as they are paired along a columnof crossover locations 620.

In general, in operation, each area over which a particular driveelectrode 606 overlaps a pickup electrode 602 in the 2D grid array, witha separation of the insulating dielectric substrate 604 is an area thatcan capture and establish a sensing location that definescharacteristics or features of a nearby fingerprint, e.g., in thevicinity above that area. Since there exist multiple sensing locationsover the area of the 2D sensor 600 grid array, multiple data pointsdefining features or characteristics of a nearby fingerprint can becaptured by the sensor 600 configuration. Thus, the sensor 600 canoperate as a planar two-dimensional sensor, where objects, such asfingers, located on or about the sensor 600 can be detected and theirfeatures and characteristics determined.

It will be understood by those skilled in the art that the disclosedsubject matter provides a biometric authentication system wherein abiometric image sensor can be incorporated into a user authenticationapparatus providing user authentication, e.g., for controlling access toone of an electronic user device or an electronically provided service.The electronic user device may comprise at least one of a portable phoneand a computing device. The electronically provided service may compriseat least one of providing access to a web site or to an email account.The biometric image sensor may be incorporated into a userauthentication apparatus providing user authentication for controllingan online transaction. The user authentication apparatus may be areplacement of at least one of a user password or personalidentification number. The user authentication apparatus may beincorporated into an apparatus providing user authentication forcontrolling access to a physical location, or providing userauthentication demonstrating the user was present at a certain place ata certain time. The user authentication apparatus may be incorporatedinto an apparatus providing at least one of a finger motion user inputor navigation input to a computing device. The user authenticationapparatus may be incorporated into an apparatus providing authenticationof the user to a user device and the performance by the user device ofat least one other task, e.g., specific to a particular finger of theuser. The user authentication apparatus may be incorporated into anapparatus providing user authentication for purposes of making anon-line transaction non-repudiatable.

It will be understood by those skilled in the art that the disclosedsubject matter may comprise a biometric imager which may comprise aplurality of sensor element traces, e.g., formed in or on a sensorsubstrate, which may be a glass or glasslike dielectric and may compriseat least a portion of a display screen, e.g., in a user device, such asa hand held user communication and/or computing defining a biometricsensing area and forming in-active pixel locations, such as are shown inFIG. 6; an auxiliary active circuit, such as the multiplexers shown inFIGS. 1, 2, 4 and 5, formed in or on the sensor substrate on theperiphery of the biometric sensing area and in direct or indirectelectrical contact with each of the plurality of sensor element traces;and the auxiliary active circuit providing a signal processing interfacebetween the plurality of sensor element traces and a remotely locatedcontroller integrated circuit, such as a sensor controller IC. Theplurality of sensor element traces may form a portion of one dimensionallinear capacitive gap biometric imaging sensor. The plurality of sensorelement traces may form the rows and columns of pixel locations in a twodimensional grid array capacitive gap biometric imaging sensor, such asis shown in 6. The auxiliary circuit may comprise a pixel locationselection circuit or a pixel signal amplification circuit such as isshown in FIG. 5. The auxiliary circuit may be mounted on the surface ofthe display screen. The auxiliary circuit further may comprise aseparate pixel location selection controller circuit such as is shown inFIG. 5.

Turning now to FIG. 7 there can be seen, partly schematically, anexample of a biometric sensor 1110 for sensing a biometric, such as afingerprint from a user finger 1120. The sensor may be formed on thesurface of a top glass 1112, which may be part of a display screen, suchas a touch screen. On the underside of the glass layer 1112 over whichthe finger 1120 of the user may be placed or swiped, may be formed alayer 1114 of material, which may be a dielectric and may be flexible,such as a film of Kapton® tape, which may have sensor elementelectrodes/traces formed on one or both opposing surfaces and may alsohave mounted thereon, e.g., by a chip on film (COF) or flip chipmounting technique a sensor controller IC 1116 to the substratecontaining the sensor element electrodes/traces. As noted in thisapplication, for some embodiments, the entire assembly may be on theorder of less than 1 mm in thickness H, e.g., on the order of 0.1 mm inthickness, especially for COF types of packaging when considered withoutthe thickness of the IC, such as when the IC is separate from thesensor. Also depending on acceptable signal level, the thickness may beon the order of 2 mm or even thicker, e.g., for flip chip mountingpackages.

FIG. 8 shows partly schematically a second configuration 1110 similar tothat of FIG. 7 wherein a molding or filling compound, e.g., epoxy 1130seals in the IC 1116 and the sides of the glass top plate 1112 andallows for the formation of electrical contacts 1132 on the sides of thebutton assembly 1110 and 1134 on the underside of the assembly 1110,which may, as explained in more detail below, be electrically connectedto the IC input/output (I/O) connectors and/or sensor electrodes/traces.

A 1D or 2D sensor on glass (SOG) can have passive elements, such asresistors or capacitors, e.g., formed into a single package, which canallow for the most flexibility, e.g., minimizing sensing location (pixelsize), border (i.e., for mechanical considerations such as bezel,lowered manufacturing costs (e.g., piggy-backing on touchscreen panelformation), and smallest form factors (height, width, etc.). Accordingto aspects of embodiments of the disclosed subject matter existingprocesses in both touch screen sensor fabrication (Young Fast) andassembly (STARs), with a few particularized steps, e.g., forming aplanarized dielectric, and metallization for flip chip constructions arereadily available.

According to aspects of embodiments of the disclosed subject matter, aquite small “round button” fingerprint sensor for a given pixel countand sensor area can be achieved, and also the flexibility exists to formany shape, e.g., round, square, square with rounded corners, etc.,complimenting a number of designs for authentication biometric sensors,especially for user mobile devices, such as those employing touchscreendisplays.

Referring again to FIGS. 7 and 8 the materials mentioned for each layerin those FIGS. can be substituted for by like material that yields thesame function(s). For instance, the glass layer 1112 can be substitutedfor by non-conductive plastic such as Polycarbonate (“PC”), Poly(methylmethacrylate) (“PMMA”), a transparent thermoplastic, often used as alightweight or shatter-resistant alternative to glass, Polyethyleneterephthalate glass (“PET”), corundum such as sapphire or ruby, etc.provided the thickness of the material is appropriately adjusted toyield adequate signal strength and thus biometric sensing through theglass 1112.

FIG. 9 shows a simplified schematic showing an X-Y sensor array 1140connecting to a controller IC 1116. The transmitter electrode traces X1,X2, X3, . . . Xn−1, Xn 1142 and the receiver electrodes/traces Y1, Y2,Y3, . . . Yn−1, Yn 1144 form a two dimensional sweep or placementbiometric sensor array.

FIG. 10 illustrates a cross sectional view of a compact construction fora 2D swipe or placement grid array fingerprint sensor array 1110, e.g.,with flip-chip bonded sensor controller IC. In this construction, therecan be, as an example, three metal layers and two isolation dielectriclayers forming a 2D sensor element layer 1114. An example of metallayout is provided in FIG. 11. An X metal layer 1150, e.g., containingthe transmitter electrodes/traces, e.g., formed on a dielectric layer1152, e.g., a flex tape, e.g., made of Kapton® tape, with a secondreceiver electrode/traces metal layer 1154 opposite the transmitterelectrode/traces 1150. An additional dielectric layer 1156 can beconnected to the sensor IC controller through ball grid array or soldergrid array balls/bumps 1160 and associated vias through the dielectriclayer 1156.

Several criteria can be utilized in selecting the pitch and/or thicknessof the transmitter and receiver metal electrode/traces 1150, 1154,dielectric 1152, 1156 material, and cross-over point size and shape,etc. in order to achieve optimum performance, ease of manufacturing, andlowest cost. For example, a screen-printed “pattern” of dielectricislands 1146, as also illustrated schematically in FIG. 12A can bescreen-printed on the “pattern” of metal transmitter or receiverelectrodes/traces 1142, 1144 in order to separate the transmitter andreceiver electrodes/traces 1142, 1144 at the crossover points 1146, witha minimum of manufacturing cost. FIG. 12B illustrates schematically acase in which the dielectric layer 1170 can be deposited, e.g., as aspin-on over a large area, and then etched back to for the rectangularor other shaped dielectric layers 1170 formed intermediate thetransmitter and receiver electrodes/traces. Contact holes 1172 can beformed in the dielectric islands 1170, e.g., with a mask and etchprocess, e.g., in order to make connection to the under-lying metallayer, e.g., the receiver layers 1144.

FIG. 13A shows a cross sectional schematic view of a glass mountedsensor array 1110 according to aspects of embodiments of the claimedsubject matter which illustrates a simplified drawing of a “compact”form factor for a 1D or 2D sensor 1110 with a controller IC 1116 mountedon a sensor electrode/trace arrangement layer 1114, e.g., as illustratedin FIG. 7 or FIG. 10 above, intermediate and mounted to a glass layer1112 and a controller IC 1116, e.g., attached to the sensor elementarrangement 1110 by a flip chip COF mounting technique.

FIG. 13B illustrates schematically an alternative similar arrangementthat can be achieved with one less layer of metal, e.g., resulting inlower cost manufacturing process. The construction in FIG. 13B may besuitable for a larger format such as on a cover-glass of the mobileunit, in which the 1D or 2D sensor 1110, which can be made oftransparent materials, plus flip-chip controller IC 1116 could belocated near an actual or virtual home button or other icon(s), sincethe opaqueness of the controller IC can be located away from the sensorelements/traces layer 1114 and thus also from the home button oricon(s). This latter arrangement, however, may lack some compactness.

FIG. 14A shows in more detail an arrangement similar to the schematic ofFIG. 13A, as is discussed in more detail in one or more of the abovenoted co-pending applications of the assignee of the presentapplication, wherein the sensor elements/traces layer, i.e., thetransmitter electrodes/traces 1142 and receiver electrodes/traces 1144,may be formed on one side of a substrate, e.g., a foldable flex tape1180. The sensor controller IC 1116 may be mounted, e.g., by flip chipmounting onto the same side or opposite side of the substrate 1180, andthe “wings” 1182, 1184 containing the transmitter electrodes/traces 1142and receiver electrodes/traces 1144 folded back over the chip mountingregion where the controller IC 1116 is mounted to form a structure likethe schematic of FIG. 7A. That is, the controller IC 1116 will be amidstthe 2D grid array sensor sensing area, mounted on one side or the otherof the region of the substrate 1180.

FIGS. 14B(1), 14B(2) and 14B(3) show this fabrication assembly processin more detail. After the transmitter electrodes/traces 1142 are formedon the “wing” 1184 and the receiver electrodes/traces 1144 are formed onthe “wing” 1182 a layer of dielectric and adhesive ordielectric/adhesive 1101 may be formed on the portion of the substrate1180 containing the sensor controller IC 1116, with perhaps onlyadhesive necessary if the sensor controller IC 1116 is mounted on theopposite side of the layer 1180 to which the adhesive is applied, withthe layer 1180 itself perhaps being a dielectric. The “wing” 1184 canthen be folded over the region 1190 containing the sensor controller IC1116. Another layer of dielectric and adhesive or dielectric/adhesive(not shown) can then be placed over the “wing” 1184 and the “wing” 1182folded over the “wing” 1184 to form the structure of FIG. 13A.

FIG. 14C shows in more detail a fabrication structure which isschematically illustrated in FIG. 13B. The sensor electrode/traces layerstructure 1414 for the transmitter electrodes/traces and the receiverelectrodes/traces structure are respectively formed on opposing sides ofa substrate 1480 to form the 2D sensor array and the sensor controllerIC 1416 is mounted on one side or the other of the substrate 1480, whichmay also contain, as illustrated, electrical connections 1400 from theremotely positioned sensor controller IC 1416, e.g., respectively, forthe transmitter electrode/traces 1142 on one side of the substrate 1480and the electrical connections 1402 between the receiverelectrodes/traces 1144 on the opposite side, brought to the same sidethrough vias in the substrate 1480. Also seen are connectors 1410 forconnecting the flexible substrate 1480 to a package or device lead framearrangement for connection of the sensor apparatus 1410 to anotherelectronic device, which may include anisotropic conductive film (“ACF”)bonding. FIG. 14C, as noted, shows a typical layout of a 2D sensor 1410with controller IC 1416 placement next to the array traces structure1414 formed on opposite sides of the substrate 1480 to illustrate theform factor shown by way of example in FIG. 13B. The bonding pads 1412can be laid out as “bonding” pads distributed around the periphery,e.g., to allow for wire bonding to the lead frame in a standard ICpackage processes.

FIG. 15 shows schematically a manufacturing process for mass producingbutton constructions according to aspects of embodiments of thedisclosed subject matter. The buttons can be formed on a glass panel1530 such that the panel 1530 forms the substrate 1520 corresponding tosubstrate 1112 in FIG. 13A, with the sensor IC 1116 attached, as thereshown, and having the electrodes/traces layer structure 1114. Eachbutton 1110 can then be individually cut from the larger glass panel1530 to form, e.g., the button of the construction shown in FIGS. 7 and13A. As an example, in FIGS. 15 and 17, circular glass button shapes maybe cut from a larger sheet of glass or other suitable material, e.g.,panel 1530 in FIGS. 15 and 1710 in FIG. 17. In the button arrangement1700 of FIG. 17, the traces (not shown), on the opposing side of theglass substrate 1710 in FIG. 17 can be connected by connectors 1704 tothe controller IC 1716, e.g., through vias (not shown) in the substrate1710 cut from the panel 1530. Some or all of the connectors 1704, e.g.,illustrated as connectors 1720 may be connected to wire bonds 1722 andsuch wire bonds 1722 in turn be connected to a connector 1724 on anotherdevice. A passive device 1706 may be connected to the glass panel 1710in FIG. 17 by a connector 1708 on the glass panel 1710, e.g., connectedto a trace (not shown) on the opposite side of the panel 1710 to thecontroller IC 1716.

FIG. 25 shows a portion of a manufacturing process for a buttonarrangement 2500 according to aspects of an embodiment of the disclosedsubject matter. The button can contain a sensor with anApplication-specific Integrated Circuit (“ASIC”) controller IC mountedon an opposite side of a substrate from the sensor traces (not shown).The IC 2516 can be mounted to a metallization layer 2520, which may bemade of deposited and etched conductive material, such as copper (Cu)forming sensor input/output (“I/O”) traces (“copper (“Cu”) side down”formed on a substrate 2504. The substrate 2504 may be formed of aflexible material coming from a reel of flexible material, which may bein the form of a flex tape or sheet (suitable for multiple buttonarrangements 2500 to be formed using the flexible material across thewidth of the flexible sheet. The IC 2516 may be mounted on the flextape/sheet by a COF mounting style, which may include an underfillsealant 2522 and may be further sealed to and adhered to the flexibletape/sheet 2504 by an encapsulant filler material, such as epoxy 2530,which may be deposited, as the flexible tape/reel 2504 moves past anencapsulation station, by, e.g., a stencil printing process.Alternatively, the fingerprint sensor sensing element electrodes/tracesmay be formed in the same copper layer 2520 as the IC I/Oelectrodes/traces.

The button arrangement 2500 may then be passed under a dielectricprinting station, or the reel can be flipped and the dielectricdeposition station positioned under the reel tape/sheet for thedeposition of a dielectric layer 2502, e.g., formed of, as an example, aresin with interspersed high dielectric constant material(s), such as bya screen printing process. The dielectric layer 2502 then forms aprotective and insulative layer over the fingerprint sensor sensingelement traces formed, e.g., by a metallization layer deposition andetch process on the surface of the flexible material tape/sheet 2504opposite from the side to which the IC 2516 is mounted. As noted above,such a process may be referred to as a copper (“Cu”) down processbecause of the position of the surface of the flexible tape/sheetreceiving the copper deposition for mounting of the IC 2516 within thebutton 2500 arrangement.

FIG. 26 illustrates as an example a “copper (‘Cu’) up” buttonarrangement 2600′. In the arrangement 2600′, the copper deposition is onthe surface of the flexible material tape/sheet 2604 on the top of thetape/sheet 2604 and, thus, above the filler material 2630 forming therest of the button 2600′ structure. The filler material 2630 is formedon the reverse side of the tape/sheet 2604. The fingerprint sensorsensing element electrodes/traces can be formed on the opposite side ofthe tape/sheet 2604 and extended (not shown) in some embodiments outsideof the button arrangement on the tape/sheet 2604 (e.g., as seen as anexample in FIGS. 21-24 and 27, for electrical connection to devices,e.g., a remote IC or a device in which the button is mounted. Such anarrangement can be referred to as a “copper (“Cu”) down” buttonarrangement.

FIG. 21 shows by way of example a Cu down button arrangement afterfurther manufacturing processes, to add material to the basic buttonarrangements formed as discussed in regard to FIGS. 25 and 26. With theCu side down, the ASIC IC 2116 can also be incorporated into the buttonstructure. Additional filler material, either of the same type as moldedin the processes described in regard to FIGS. 25 and 26 or of adifferent material with similar or the same performance characteristicsmay be added, e.g., to the right side of the button arrangement 2100 asshown in FIG. 21. This additional material may be added by putting thebutton arrangement 2500 of FIG. 25 into an injection molding machine toadd this additional material encapsulating an extension of the Cu downflex tape 2504 and copper metallization layer 2520. Such an extensionmay further extend outside of the package 2200 for the placement of leadlines 2212 as illustrated in FIG. 22.

FIG. 23 illustrates a formation, e.g., in an injection molding machineof added material, e.g., the same epoxy as for the filler 2330 as inFIGS. 25 and 26, or some other suitable material, on both ends of thecore button arrangements 2500 of FIGS. 25 and 26. This may be utilizedto form a cavity with side walls 2340 around the periphery of the buttonpackage 2300. The cavity may then be further filled with a liquid resinof the type deposited in the processes described in regard to FIGS. 25and 26 to fill the cavity with the dielectric material 2302.

FIG. 24 illustrates another example button arrangement package formedsimilarly to the one illustrated in FIG. 21 with the exception of thedielectric layer 2102 forming a layer 2450 that also includes or ismixed with or has deposited on top a suitable adhesive 2450 to allow forthe placement of another dielectric layer 2460 formed from, e.g.,corundum, otherwise known as a aluminum oxide (“αAl2O3”), with the αrepresenting trace amounts, typically contributing to color, and alsofamiliarly known as sapphires and rubies. Such material can be easilydeposited in thin layers by thin film deposition processes known in theart. This dielectric layer can be extremely sturdy and dielectric ineffect, while very thin at the same time. It will be understood by thoseskilled in the art that such thin film deposition may eliminate the needfor some or all of the adhesive layer 2450. It will be understood thatthe high dielectric constant material plate, which may be attached withthe thin layer of adhesives 2450 after core button assembly 2100construction, may also be formed by thin slices of crystalline forms ofαAl2O3 (corundum). Such a dielectric layer, whether thin film depositedor placed as a slice(s) may be on the order of 100 μm in thickness. Alsopossible is deposition through the extrusion of a thin plastic platewith interspersed high dielectric constant materials.

FIG. 27 illustrates an example of a button arrangement package 2700wherein the dielectric material 2702 is added to the injection moldingor like process when the further filler material 2730 is formed aroundthe extension of the flex tape 2704 and copper metallization layer 2720.Alternatively the dielectric material 2702 covering the extension of theflex tape 2704 may be added and shaped after the addition of theadditional filler material 2730. As an example, a molding with a resinmaterial that is pre-composited with the high dielectric constantmaterials may be utilized after the molding extending the fillermaterial 2730 as discussed above in regard to FIGS. 21-24 or as asubstitute for the step of depositing the resin as described in regardto FIGS. 25 and 26.

The aspects of the disclosed subject matter as described thus far canthus be fabricated in large volume for the consumer market. As anexample of process flow may consist of major steps, such as:

-   -   start with a glass panel of desired thickness, e.g., of panel        dimensions that are optimum for a given form factor;    -   deposit metal layer one, mask and etch, or screen-print a        “patterned” metal layer one of transmitter electrodes/traces of        a given width and pitch, or the like;    -   deposit dielectric layer one, mask, and etch, or screen-print        “patterned” isolation islands, or the like;    -   deposit metal layer two, mask and etch, or screen-print a        “patterned” metal layer two or receiver electrodes/traces of a        given width and pitch, or the like;    -   deposit dielectric layer two;    -   planarize dielectric layer two to achieve flatness required for        flip-chip;    -   flip-chip bond the controller IC; and    -   encapsulate the button with, e.g., a molded plastic enclosure.

A low-cost process flow may be as follows:

-   -   start with a glass panel of a desired thickness, e.g., of panel        dimensions that are selected for a given form factor;    -   screen-print a “patterned” metal layer one formed of        electrodes/traces;    -   screen-print “patterned” isolation islands;    -   screen-print a “patterned” metal layer two formed of        perpendicular electrodes/traces;    -   deposit dielectric layer two;    -   planarize the dielectric layer two to achieve flatness required        for flip-chip;    -   etch or otherwise form appropriate vias;    -   flip-chip bonding controller IC; and    -   mold the plastic enclosure.

Another variation of a low cost process flow, which can, e.g., allow forintegration of passive components into the confines of the structuralarrangement, such as is shown by way of an example in FIG. 20, may be asfollows:

-   -   start with glass panel of desired thickness, e.g., of panel        dimensions that are selected for a given form factor;    -   laminate a thin copper foil to the glass panel, e.g., using a        “high temperature” adhesive (ADH#1);    -   pattern and etch the copper foil metal layer one;    -   deposit dielectric layer one, mask and etch; e.g. to form the        dielectric islands;    -   screen-print a “patterned” metal layer two of electrodes/traces        formed perpendicularly to the electrodes/traces of layer one;    -   deposit dielectric layer two;    -   planarize the dielectric layer two in order to achieve flatness        required for flip-chip;    -   bond the flip-chip controller IC;    -   place passives as appropriate, e.g., pre-soldered passives onto        the lead-frame;    -   wire-bond I/O leads as appropriate to the lead-frame; and    -   mold the plastic enclosure.

The ADH#1 material may include coloration and/or decorative additive(s)to enhance the cosmetic features of the finished product, e.g., asviewed through the topside glass. Most high dielectric constantmaterials are available in a powder form, and the powder can be mixedfollowing conventional mixing techniques to disperse the respectivepowder(s) in various resins such as polyurethane or acrylic resins. Thiscan be done in a fashion similar to color pigments being dispersed ininks, e.g., by using an appropriate dispersant and/or by pre-treatingthe appropriate surface(s). The powders may also be combined into moltenresin and/or repelletized for plastic molding or extruded to producesheets of a desired thickness. Other high dielectric constant materialscan be found in bulk crystal form which can then be cut and polished tobe used as a plate, e.g., placed on top of a sensor.

FIG. 16 illustrates a cross sectional schematic view of a sensorelectrode/trace arrangement 1600 as a variation of FIG. 13A. In FIG. 16the transmitter electrodes/traces 1620 may be formed with intermediateopenings 1650, through which the orthogonal receiver electrodes/traces1640 may pass, with the openings 1650 and receiver electrodes/traces1640, and portions of the transmitter electrodes/traces 1620 covered bydielectric islands 1652 also along the extension of theelectrodes/traces 1620. The respective transmitter electrodes/traces1620 may be bridged by jumpers 1630, which may be made of silver andmay, in turn, be covered with additional dielectric islands 1610. Thesensor controller IC 1616 may be mounted in a flip chip fashion by bumps1602 which may be connected to, on the one hand, a metal lead 1604 fromthe transmitter electrode/trace 1620 to the sensor controller IC 1616and, on the other hand, by a metal lead 1606, to a passive 1670separated from the respective transmitter electrode/trace 1620 bydielectric 1660. The entire structure can be formed on the glass touchscreen layer display glass 1600. According to aspects of embodiments ofthe disclosed subject matter, as noted above, a round area sensor onglass, e.g., with an 8 mm or 9 mm diameter and a 0.6 mm or 0.7 mmthickness is possible, integrating a system in plastic (“SIP”) module.

A chip on glass (“COG”) package lead frame according to aspects of thedisclosed subject matter may have several options such as allowing forcontact pads to be placed around the side of the button package.Alternatively, the contact pads may be placed at the bottom of thebutton, with the top formed by glass or other suitable transparentplastic materials such as epoxies and wherein the glass may alsoencapsulate the sensor IC and connections, such as wire bond connectionsto the bottom of the button, e.g., through connectors formed in vias.

Another COG arrangement may include a glass bottom substrate with asensor controller IC 1616 connected to the glass through flip chip bumpswhich may be encapsulated in an ACF or non-conductive connective film(“NCF”). The glass may also be connected to a flex cable which may havetransmitter and receiver electrode(s)/trace(s) formed on opposite sidesthereof and connected to the glass by ACF bonding.

A system in a package (“SIP”) 1900, as illustrated in FIGS. 19A and 19Bmay be formed with passive components 1940 in the package 1900. Thesystem 1900 may have circular transmitter and or receiver electrodes1904, one of which is illustrated schematically in FIGS. 19A and 19B. Ascan be seen by way of example in FIG. 19B, the electrode 1904 may beconnected to the glass 1902 by ACF bonding 1910 and to the passives 1940by conductive bonding 1930. The sensor IC may be connected to the glass1902 by bumps 1922 and bonding pads 1920 surrounded by ACF/NCF bonding1924. The entire system may be encapsulated by molding/filling plastic1960. This can provide for a large sensor area with minimum border areaand no need for a printed circuit board arrangement, low cost bondingand a compact form. Such a button can be round in form, be attached by alead frame and have capacitors or other passives 1950 in the button, andmay, as noted above, include wire bonding. Such may be seen by way ofexample in FIG. 20 where the electrode 2004 may be connected to theglass 2002 by wire bonding pads 2080, 2082 and connecting wire bonds2086.

Addition of a sensor signal boosting structure by mixing in highdielectric constant materials to sensor packaging or coating materialscan result in signal to noise ratio improvement and thus improvement ofoverall signal strength can be accomplished by, e.g., diffusing higherdielectric particles in coatings/protective layers/moldings and the likethat are intermediate a finger of a user and the traces forming thecapacitive sensor sensing elements. Thus, within a chip on film (COF)structure or a ball grid array (BGA) sensor package, both of which maybe utilized for 1D linear array capacitive gap sensors and 2D sensorelement grid arrays, swiped and placement, such packaged COF or BGAsensors can have components which can be integrated into, e.g., usermobile devices, such as cell phones, smart phones, pads, tablets,personal digital assistants (PDAs) and other applicable consumerelectronic devices can be fabricated using multiple layers of protectivedielectric material, such as molding or epoxy filling, or stackingmultiple layers of hard materials for the desired hardness, durabilityand possibly other aesthetics, such as if the materials are transparentor pigmented or the like.

In passive capacitive biometric sensors, e.g., a fingerprint sensor, areceived sensor signal can be affected by any such materials that areincorporated into any protective/decorative coating. Such a coatingcould form part of an insulating layer and/or a molded structure, e.g.,as part of a housing or package for the sensor sensing elements andperhaps electronics, etc. When such material is situated between thesensor elements, such as may form a 1D linear array capacitive gapsensor array or a 2D grid array, swiped or placement sensor, and thefinger of a user during the operation of the sensor, i.e., as the fingeris placed on the sensor array or swiped over the sensor array, in mostcases, the thicker the topping materials are, the lower the sensoroutput signal level. On the other hand, for mechanical durability andother reasons, such as electrical isolation and the like, thick and hardmaterials may be desirable to be placed over the sensor sensingelements. However, the thickness is, as noted, limited due to signaldegradation. According to aspects of the disclosed subject matter suchshortcomings in the art are at least alleviated. The sensor sensingelements, i.e., electrodes/traces may be formed on an a flexible tapelayer adjacent the harder coating material separated from the userfinger by the harder coating material.

The received signal across a capacitive gap in a 1D sensor or at thereceiver sensor sensing element(s) in a 2D grid array sensor at a givenimage pixel sensing location on the grid array is largely effected bythe capacitance between the user's finger and the receiver element. Thisis in turn affected by the type and thickness of the material betweenthe finger and the receiver sensing element, or in some embodiments thesensing transmitter element. The conductive sensor sensing elements,e.g., made of copper (Cu) could be formed under the flex layer, and thusthe dielectric effect of the flex layer would need to be factored in aswell.

According to aspects of embodiments of the disclosed subject matter, thesignal to noise ratio may be improved, e.g., by diffusing higherdielectric constant material(s) into the protectivecoating/molding/filling dielectric material so as to, e.g., allow morefield flux to reach the finger of the user. That is the capacitivedielectric rating can be decreased so more electric field reaches thefinger and the impact of the capacitance of the finger on the receivedfield (i.e., whether there is a ridge or valley at the particular pixellocation can be more easily detected for an given applied signalstrength transmitted from the sensor transmitter element(s) in effect.Lower dielectric number materials such as a vacuum (the lack of anymaterial), air, Teflon®, polyimide, silicon dioxide have low dielectricconstant numbers (the ratio of the permissivity of the material inrelation to air). These generally form better insulators between theconductive plates of a capacitor, with the lower numbers formingcapacitors with higher capacitive impedance. Higher dielectric constantmaterials such as TiO2, 86-173, strontium titanium oxide (STO), StTiO3,310 and barium strontium titanium oxide (BSTO), BaStTiO3, 500 can beused as suitable diffusants/dispersants. As thecoating/protective/insulative layer becomes thicker, morediffusant/dispersant of the type denoted may be utilized tomaintain/increase signal to noise ratio.

3M™ Scotch-Weld™ sold under the name epoxy potting compound, DP270 is arigid, two-part epoxy adhesive potting compound, with a 1:1 mix ratio,70 minute work life and reaches handling strength from a relativelyviscous initial state in approximately 3 hours. The material isnon-corrosive to copper and finds applications in, e.g., solar energy,wind energy, composites and electronics applications for bonding,gluing, joining, attaching, assembling, encapsulating, potting andsealing. Such an adhesive may be used according to aspects of someembodiments of the disclosed subject matter.

Ferro Electronic Material Systems offers a wide variety of ceramicmaterials to improve the performance of organic compounds used in abroad range of applications. These additives can enhance conductivity,improve high-frequency performance, alter permittivity, modify sealingcharacteristics, improve flame resistance, improve moisture resistanceand provide many other benefits. Such Ferro additives are examples offilled polymers. The table below lists specific products andapplications. Additives can include: Barium Strontium Titanate,Strontium Titanate, Titanium Dioxide; Barium Titanate; Bismuth Trioxide;Barium Zirconate; Zirconium Oxide; Ceramic Powders. Each application canrequire specific physical characteristics and variables can be adjustedto meet the needs for filled polymers applications. For example, varyingthe amount of barium and strontium in an additive can shift the CuriePoint of the composite material, e.g., to enhance performance over aspecific temperature range. Table I discloses possible materials for useas high dielectric additives.

TABLE 1 Particle Size Surface Ceramic Dist (μm) Area Powders TypicalApplication D90 D50 D10 (m²/g) 104-2 Plastic filler 3.3 0.8 0.34 10.51Zirconium Oxide I 119 Barium Plastic seals and 3.1 1.0 0.61 4.16Zirconate molding 203-4 Filled polymers to 1.7 1.1 0.65 4.7 Titaniumreduce dielectric Dioxide constant and promote high frequencyperformance Ticon ® HG Filled polymers to 4.5 3.0 1.5 2.3 Titaniumreduce dielectric Dioxide constant and promote high frequencyperformance Ticon ® CG Filled polymers to 7.2 4.0 1.9 — Titanium reducedielectric Dioxide constant and promote high frequency performance 217Calcium Polymer antennas and 4.2 1.6 0.75 4.55 Titanate other telecomapplications 218 Strontium Filled polymers to 4.6 2.0 0.93 1.81 Titanatepromote high fre- quency performance; toners and anticoun- terfeitingapplications Ticon ® 55 Filled polymers 2.9 1.1 0.5 4.3 Strontium topromote high Titanate frequency performance 219-6A Dielectric constant2.1 1.3 0.8 2.1 Barium booster for filled Titanate circuit boards,electroluminescent lights and other filled applications Ticon ® CDielectric constant 3.8 1.5 0.6 2.4 Barium booster in filled Titanatecircuit boards and other filled applications Ticon ® HPBElectroluminescent 2.1 1.0 0.4 3.2 Barium lighting Titanate BST BariumFilled polymers to Strontium promote targeted Titanate high-frequencyperformance 320A Bismuth Density modifier 16 6.1 1.5 0.2-0.5 Trioxidefor plastics AD143N Dielectric constant 1.9 0.9 0.5 3 Ceramic booster infilled Powder circuit boards and other filled applications

According to aspects of embodiments of the disclosed subject mattersuitable high dielectric constant materials can be used to incorporateinto selected resins for sensor packaging. For the ease of dispersions,sub-micron or even finer nanoparticles can provide excellent candidatesto fill the resins. One can determine the mass loading of highdielectric constant materials, where the mass loading % is determinedbased on viscosity requirements and molding techniques. If additionalsteps such as polishing or grinding of the signal boosting structure(SBS) are required, consideration of such subsequent process steps canbe taken. There are many ways to create the SBS, after completediffusion of high dielectric constant materials: 1) coating/printing ofmixed liquid resin, 2) injection molding, 3) cavity filling, 4) plateattachment, etc. These steps could be considered and selected, based onsensor design and integration needs. A uniformly thick SBS may berequired or at; least preferred across the full length of the sensor andto be able to reproduce consistent thickness from one packaged sensor toanother. Additional layers can be incorporated on top of the SBS foraesthetic purposes. The final layers should not significantly alter thesensor performance yet survive through a series of reliability testswhich are defined by customers.

FIG. 22 illustrates schematically an arrangement 2250 wherein a sensorcontroller IC chip can be connected to a substrate 2210. This may thenbe connected to another module by lead lines 2212 formed on thesubstrate 2210. The IC may be connected to the substrate 2210 by bondingpads 2220, which may, in turn, be connected to primary and secondaryreceiver traces 2202, 2204 and transmitter traces at the locations 2220of the bonding pads, since the electrical traces as illustrated in FIG.22 are on the same side of the substrate 2210 as the IC mounting pads2220 and, therefore, the IC itself.

Methods for manufacturing any of the various devices disclosed can besummarized as follows:

-   -   Select suitable high dielectric constant materials to        incorporate into selected resins for sensor packaging. For the        ease of dispersions, sub-micron or even finer nanoparticles are        the excellent candidates to fill the resins.    -   Determine mass loading of high dielectric constant materials.        Mass loading % is determined based on viscosity requirements and        molding techniques. If additional steps such as polishing or        grinding of the signal boosting structure (SBS) are required,        consideration of such subsequent process steps must be taken.    -   There are many ways to create the SBS, after complete diffusion        of high dielectric constant materials as shown, e.g., in FIGS.        19-24: 1) coating/printing of mixed liquid resin, 2) injection        molding, 3) cavity filling, 4) plate attachment, etc. These        steps could be considered and selected, based on sensor design        and integration needs. It is critical to have a uniformly thick        SBS across the full length of the sensor and to be able to        reproduce consistent thickness from one packaged sensor to        another.    -   Additional layers can be incorporated on top of the SBS for        aesthetic purposes. The final layers should not significantly        alter the sensor performance yet survive through a series of        reliability tests which are defined by customers.

It will be understood that a biometric object sensor button arrangementcore and method of forming the same is disclosed which may comprise aflex material layer; a sensor controller IC mounted on one side of theflex material layer; a metallization layer comprising a plurality ofsensor sensing element traces and controller IC input/output tracesformed on at least one side of the flex material layer, each inelectrical connection with controller IC; an encapsulation layerencapsulating the controller IC to one of the flex material layer andthe metallization layer; and a protective layer covering one of the flexmaterial layer and the metallization layer on a surface opposite fromwhere the controller IC is mounted, comprising a dielectric materialdispersed with at least one high dielectric material utilizing adispersant. The biometric object sensor button may further comprise afingerprint sensor button. The metallization layer may comprise a firstmetallization layer formed on a first surface of the flex materialcomprising the sensor sensing element traces and a second metallizationlayer formed on a second surface of the flex layer opposing the firstsurface of the flex layer and comprising at least some of the controllerIC input output traces. The button arrangement core may further comprisean extension of the flex layer and the metallization layer extendingfrom the encapsulation layer and a further encapsulation of theextension of the flex layer from the button arrangement core and theextension of the metallization layer from the button arrangement core toform a button arrangement package. A further encapsulation of theextension of the flex layer and a further deposition of dielectricmaterial on the metallization layer may be included to form a buttonarrangement package. The button arrangement core may further comprise anadhesive layer covering the one of the flex layer and the metallizationlayer and the extension of the encapsulation of the flex layer and themetallization layer; and a layer of dielectric material adhered to theadhesive layer, which may be corundum and may be deposited by thin filmdeposition or as a thin crystalline sheet(s). The method may compriseforming a flex material layer; mounting a sensor controller IC on oneside of the flex material layer; forming a metallization layercomprising a plurality of sensor sensing element traces and controllerIC input/output traces formed on at least one side of the flex materiallayer, each in electrical connection with controller IC; encapsulatingthe controller IC in an encapsulation layer formed on one of the flexmaterial layer and the metallization layer; and forming a protectivelayer covering one of the flex material layer and the metallizationlayer on a surface opposite from where the controller IC is mounted,comprising a dielectric material dispersed with at least one highdielectric material utilizing a dispersant.

While preferred embodiments of the present invention have been shown anddescribed herein, it will be obvious to those skilled in the art thatsuch embodiments are provided by way of example only. Numerousvariations, changes, and substitutions will now occur to those skilledin the art without departing from the invention. It should be understoodthat various alternatives to the embodiments of the invention describedherein may be employed in practicing the invention. It is intended thatthe following claims define the scope of the invention and that methodsand structures within the scope of these claims and their equivalents becovered thereby.

The invention claimed is:
 1. A biometric imager comprising: a pluralityof sensor elements formed in or on at least a portion of a displaydefining a biometric sensing area and forming pixel locations; and anauxiliary active circuit formed outside the biometric sensing area andin direct or indirect electrical contact with each of the plurality ofsensor elements, wherein the auxiliary active circuit comprisesthin-film transistors (TFTs) formed on a glass substrate, and whereinthe auxiliary active circuit is configured to provide a signalprocessing interface between the plurality of sensor elements and asilicon controller integrated circuit.
 2. The biometric imager of claim1, wherein the plurality of sensor elements form a portion of aone-dimensional linear capacitive gap biometric imaging sensor.
 3. Thebiometric imager of claim 1, wherein the plurality of sensor elementsform rows and columns of pixel locations in a two-dimensional grid arraycapacitive gap biometric imaging sensor.
 4. The biometric imager ofclaim 1, wherein the auxiliary active circuit comprises a pixel locationselection circuit.
 5. The biometric imager of claim 1, wherein theauxiliary active circuit comprises a pixel signal amplification circuit.6. The biometric imager of claim 1, wherein the auxiliary active circuitis disposed on a surface of the display.
 7. The biometric imager ofclaim 1, wherein the auxiliary active circuit comprises a separate pixellocation selection controller circuit.
 8. A method of biometric imagingcomprising: providing a plurality of sensor elements formed in or on atleast a portion of a display defining a biometric sensing area andforming pixel locations; providing an auxiliary active circuit formedoutside the biometric sensing area and in direct or indirect electricalcontact with each of the plurality of sensor elements, wherein theauxiliary active circuit comprises thin-film transistors (TFTs) formedon a glass substrate, and wherein the auxiliary active circuit isconfigured to provide a signal processing interface between theplurality of sensor elements and a silicon controller integratedcircuit.
 9. The method of claim 8, wherein the plurality of sensorelements form a portion of a one-dimensional linear capacitive gapbiometric imaging sensor.
 10. The method of claim 8, wherein theplurality of sensor elements form rows and columns of pixel locations ina two-dimensional grid array capacitive gap biometric imaging sensor.11. The method of claim 8, wherein the auxiliary active circuitcomprises a pixel location selection circuit.
 12. The method of claim 8,wherein the auxiliary active circuit comprises a pixel signalamplification circuit.
 13. The method of claim 8, wherein the auxiliaryactive circuit is mounted to a surface of the display.
 14. The method ofclaim 8, wherein the auxiliary active circuit further comprises aseparate pixel location selection controller circuit.
 15. The biometricimager of claim 1, wherein the auxiliary active circuit and theplurality of sensor elements are both disposed on the glass substrate.16. The biometric imager of claim 1, wherein the glass substrate ismultiplexer strip glass and the plurality of sensor elements is disposedon array glass, and wherein the multiplexer strip glass and the arrayglass are attached.
 17. The biometric imager of claim 16, wherein anelectrode pitch of the auxiliary active circuit is matched to a row andcolumn pitch of the plurality of sensor elements.
 18. The method ofclaim 8, wherein the auxiliary active circuit and the plurality ofsensor elements are both disposed on the glass substrate.
 19. The methodof claim 8, wherein the glass substrate is multiplexer strip glass andthe plurality of sensor elements is disposed on array glass, and whereinthe multiplexer strip glass and the array glass are attached.
 20. Themethod of claim 19, wherein an electrode pitch of the auxiliary activecircuit is matched to a row and column pitch of the plurality of sensorelements.